2.3 Understanding Sources

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Understanding types of sources helps you use your sources

[1]Scholarly Articles as Sources

Articles in scholarly journals are valued for several reasons. First, they are usually trustworthy because their publication process includes a peer review that helps ensure their accuracy and contribution to their disciplines. In addition, they often contain the first reports of new research, which makes their sections on methodology, data, analysis, and interpretation primary sources. Sometimes they instead consist of literature reviews which are summaries of multiple research studies done in the past on particular subjects of current interest. That makes those articles very helpful secondary sources.

Peer-Reviewed Sources

The most-respected scholarly journals are peer-reviewed, which means that experts in their field other than the author and editor check out each article before it can be published. It’s their responsibility to help guarantee that new material is presented in the context of what is already known, that the methods the researcher used are the right ones, and that the article contributes to the field.

For those reasons, peer-reviewed articles are more likely to be credible. Peer-reviewed journal articles are the official scholarly record, which means that if it’s an important development in research, it will probably turn up in a journal article eventually.

Parts of a Scholarly Article

The articles you use for your assignments must also be relevant to your research question—not just credible. Reading specific parts of an article can help save you time as you decide whether an article is relevant.

Reading a scholarly article usually takes some effort. According to Dr. Jennifer Raff, here is how you should do it.[2]

Reading a scientific paper is a completely different process from reading an article about science in a blog or newspaper. Not only do you read the sections in a different order than they’re presented, but you also have to take notes, read it multiple times, and probably go look up other papers in order to understand some of the details. Reading a single paper may take you a very long time at first, but be patient with yourself. The process will go much faster as you gain experience.

The type of scientific paper I’m discussing here is referred to as a primary research article. It’s a peer-reviewed report of new research on a specific question (or questions). Most articles will be divided into the following sections: abstract, introduction, methods, results, and conclusions/interpretations/discussion.

Before you begin reading, take note of the authors and their institutional affiliations. Some institutions (e.g. University of Texas) are well-respected; others (e.g. the Discovery Institute ) may appear to be legitimate research institutions but are actually agenda-driven. Tip: google “Discovery Institute” to see why you don’t want to use it as a scientific authority on evolutionary theory.

Also take note of the journal in which it’s published. Be cautious of articles from questionable journals , or sites that might resemble peer-reviewed scientific journals but aren’t (e.g. Natural News).

Step-by-Step Instructions for Reading a Primary Research Article

1. Begin by reading the introduction, not the abstract.

The abstract is that dense first paragraph at the very beginning of a paper. In fact, that’s often the only part of a paper that many non-scientists read when they’re trying to build a scientific argument. (This is a terrible practice. Don’t do it.) I always read the abstract last, because it contains a succinct summary of the entire paper, and I’m concerned about inadvertently becoming biased by the authors’ interpretation of the results.

2. Identify the big question.

Not “What is this paper about?” but “What problem is this entire field trying to solve?” This helps you focus on why this research is being done. Look closely for evidence of agenda-motivated research.

3. Summarize the background in five sentences or less.

What work has been done before in this field to answer the big question? What are the limitations of that work? What, according to the authors, needs to be done next? You need to be able to succinctly explain why this research has been done in order to understand it.

4. Identify the specific question(s).

What exactly are the authors trying to answer with their research? There may be multiple questions, or just one. Write them down. If it’s the kind of research that tests one or more null hypotheses , identify it/them.

5. Identify the approach.

What are the authors going to do to answer the specific question(s)?

6. Read the methods section.

Draw a diagram for each experiment, showing exactly what the authors did. Include as much detail as you need to fully understand the work.

7. Read the results section.

Write one or more paragraphs to summarize the results for each experiment, each figure, and each table. Don’t yet try to decide what the results mean; just write down what they are. You’ll often find that results are summarized in the figures and tables. Pay careful attention to them! You may also need to go to supplementary online information files to find some of the results. Also pay attention to:

  • The words “significant” and “non-significant.” These have precise statistical meanings.
  • Graphs. Do they have error bars on them? For certain types of studies, a lack of confidence intervals is a major red flag.
  • The sample size. Has the study been conducted on 10 people, or 10,000 people? For some research purposes a sample size of 10 is sufficient, but for most studies larger is better.

8. Determine whether the results answer the specific question(s).

What do you think they mean? Don’t move on until you have thought about this. It’s OK to change your mind in light of the authors’ interpretation — in fact, you probably will if you’re still a beginner at this kind of analysis — but it’s a really good habit to start forming your own interpretations before you read those of others.

9. Read the conclusion/discussion/interpretation section.

What do the authors think the results mean? Do you agree with them? Can you come up with any alternative way of interpreting them? Do the authors identify any weaknesses in their own study? Do you see any that the authors missed? (Don’t assume they’re infallible!) What do they propose to do as a next step? Do you agree with that?

10. Go back to the beginning and read the abstract.

Does it match what the authors said in the paper? Does it fit with your interpretation of the paper?

11. Find out what other researchers say about the paper.

Who are the (acknowledged or self-proclaimed) experts in this particular field? Do they have criticisms of the study that you haven’t thought of, or do they generally support it? Don’t neglect to do this! Here’s a place where I do recommend you use Google! But do it last, so you are better prepared to think critically about what other people say.

Finding Scholarly Articles

Most scholarly articles are housed in specialized databases. Libraries (public, school, or company) often provide access to scholarly databases by paying a subscription fee for patrons. For instance, CSC Libraries provide access to many databases via its Research Databases List which is available for free to people affiliated with the college. You can search for a journal title in these databases or view a list of databases by subject. For more information, including how to search databases, see section 2.1 and the CSC Library Tutorial page.

News as a Source

News sources can provide insights that scholarly sources may not or that will take a long time to get into scholarly sources. For instance, news sources are excellent for finding out people’s reactions, opinions, and prevailing attitudes around the time of an event.

So whether news sources are good for your assignment depends on what your research question is.

News is a strange term because even when the information is old, it’s still news. Some sources are great for breaking news, some are great for aggregated (or compiled) news, and others are great for historical news.

While news was transmitted for centuries only in newspapers, news is now transmitted in all formats: via radio, television, and the Internet, in addition to print. Even most newspapers have Internet sites today.

News must be brief because much of it gets reported only moments after an event happens. News reports occur early in the Information Lifecycle.

When Are News Sources Helpful?

  • You need breaking news or historical perspectives on a topic (what people were saying at the time).
  • You need to learn more about a culture, place, or time period from its own sources.
  • You want to keep up with what is going in the world today.

When Are News Sources of Limited Use?

  • You need very detailed analysis by experts.
  • You need sources that must be scholarly or modern views on a historical topic.

Mainline and Non-Mainline News Sources

Mainline American news outlets stick with the tradition of trying to report the news as objectively as possible. That doesn’t mean their reports are perfectly objective, but they are more objective than the non-mainline sources. As a result, mainline news sources are more credible than non-mainline sources.

Some examples of mainline American news outlets

  • The New York Times
  • The Washington Post
  • The Boston Globe
  • The Chicago Tribune,
  • The Los Angeles Times
  • ABC News
  • CBS News
  • NBC News
  • PBS News
  • NPR News

News from non-mainline American news outlets is often mixed with opinions. One way they frequently exhibit bias is that they leave out pertinent facts.

Some examples of non-mainline American news outlets

  • MSNBC
  • Fox News
  • Gawker
  • Reddit.

Types of News Sources

Press Services—News outlets (print, broadcast, and online) get a lot of their news from these services, such as Reuters or Associated Press (AP), which make it unnecessary for individual outlets to send their own reporters everywhere. Services are so broadly used that you may have to look at several news outlets to get a different take on an event or situation.

News aggregators—Aggregators don’t have reporters of their own but simply collect and transmit the news reported by others. Some sources pull news from a variety of places and provide a single place to search for and view multiple stories. You can browse stories or search for a topic. Aggregators tend to have current, but not archival news. Google News and Yahoo News are examples.

Newspaper sites – Many print newspapers also have their own websites. They vary as to how much news they provide for free.

News Databases – Search current, recent, and historical newspaper content in databases provided free by libraries. CSC Libraries offers several news databases to students, staff, and faculty. They include:

  • Newsbank: America’s News: Provides access to information on people, issues, and events in the local area and around the country. From EBSCOhost.
  • Newspaper Source Plus: Provides full-text national & international newspaper coverage from more than 860 newspapers, providing more than 35 million full-text articles. Features more than 857,000 television and radio news transcripts. From EBSCOhost.
  • Newswires: Provides near real-time access to top world-wide news from Associated Press, United Press International, PR Newswire, Xinhua, CNN Wire, and Business Wire on a continuous basis while monitored by EBSCO, and relevant results are provided when users enter searches in EBSCOhost. Includes AP Financial News, AP Top News, AP WorldStream, AP U.S. Politics & Government, AP 50 State Reports, UPI Security Industry, UPI Emerging Threats, UPI Business, UPI Entertainment, UPI Sports, UPI Top News, Arabia 2000, and more. End users can immediately access the full-text of the web content, by following the link in the record. The index to the full-text content in EBSCO Newswires is held for a rolling 30-day archive by EBSCO, so users can enjoy the previous 30 days of news relating to their search interests. From EBSCOhost

Broadcast News Sites – Although broadcast news (from radio and television) is generally consumed in real time, such organizations also offer archives of news stories on their websites. However, not all of their articles are provided by their own reporters: some originate from the press services, Reuters, and AP.

Activity: One-Minute World News from the BBC

Visit BBC’s Video area and watch their One-minute World News to get a quick update on the world’s major news stories.

Social Media – Most of the news outlets listed above contribute to Twitter and Facebook. It’s customary for highly condensed announcements in this venue to lead you back to the news outlet’s website for more information. However, how credible tech companies such as Facebook, Twitter, and Google are with news is in serious doubt due to recent issues with how secure the platforms are and their ability to detect and prevent false news from being created and/or spreading.

Blogs – Sometimes these are good sources for breaking news, as well as commentary on current events and scholarship. Authors who write more objectively elsewhere can share more insights and opinions, more initial questions and findings about a study before they are ready to release definitive data and conclusions about their research.

Citizen Journalism – A growing number of sites cater to those members of the general public who want to report breaking news and submit their own photos and videos on a wide range of topics. The people who do this are often referred to as citizen journalists.

Examples of such sources include CNN iReport, and reddit. For more details on the history and development of citizen journalism, including addressing some of the pros and cons, read Your Guide to Citizen Journalism.

Data as Sources

Using data as sources can help with all of your research project’s information needs:
  • Learn more background information.
  • Answer your research question. (The evidence that it provides can help you decide on the best answer for your question.)
  • Convince your audience that your answer is correct. (it often gives you evidence that your answer is correct.)
  • Describe the situation surrounding your research question.
  • Report what others have said about your research question.

Activity: Example of Data

Check out this very detailed data about frozen lasagna. Did you ever think this much data was available? Are there elements new to you? How might you use such data?

What is data?

The word means many things to many people. (Consider “data” as it relates to your phone contract, for instance)

For our purposes, a definition we like is “units of information observed, collected, or created in the course of research.”[3]

Data observed, collected, or created for research purposes can be numbers, text, images, audio clips, and video clips. But in this section on using data as sources, we’re going to concentrate on numerical data.

TIP: From the Latin
Data is the plural of datum. (It’s similar to how media is the plural of medium.)

Sometimes data is actually necessary to answer research questions, particularly in the social sciences and life and physical sciences.

For instance, data would be necessary to support or rule out these hypotheses:

  • More women than men voted in the last presidential election in a majority of states.
  • A certain drugs shows promising results in the treatment of pancreatic cancer.
  • Listening to certain genres of music lowers blood pressure.
  • People of certain religious denominations are more likely to find a specific television program objectionable.
  • The average weight of house cats in the United States has increased over the past 30 years.
  • The average square footage of supermarkets in the United States has increased in the past 20 years.
  • More tomatoes were consumed per person in the United Kingdom in 2015 than in 1962.
  • Exploding volcanoes can help cool the planet by spewing sulfur dioxide, which combines with water vapor to make reflective aerosols.

So, using numeric data in those portions of your final product that require evidence can really strengthen your argument. At other times, even if data is not actually necessary, numeric data can be particularly persuasive and sharpen the points you want to make in other portions of your final product devoted to, say, describing the situation surrounding your research question.

For example, for a term paper about the research question “Why is there a gap in the number of people who qualify for food from foodbanks and the number of people who use foodbanks?,” you could find data on the website of Feeding America, the nation’s largest network of foodbanks. Some of that data may be the number of people who get food from a foodbank annually, with the number of seniors and children broken down. That data won’t answer your research question, but it will help you describe the situation around that question and help your audience develop a fuller understanding (i.e. context).

Similarly, for a project with the research question “How do some birds in Australia use ‘smart’ hunting techniques to flush out prey, including starting fires?,” you might find a journal article with data about how many people have observed these techniques and estimates of how frequently the techniques are used and by how many bird species.

Obtaining Data

There are two ways of obtaining data:

  • Obtain data that already has been collected and analyzed. That’s what this section will cover.
  • Collect data yourself. This can include activities such as making observations about your environment, conducting surveys or interviews, directly recording measurements in a lab or in the field, or even receiving electronic data recorded by computers/machines that gather the data. You will more than likely explore these activities in the courses you take.

Finding Data in Articles, Books, Web Pages, and More

Numeric search data can be found all over the place. A lot of it can be found as part of other sources such as books, journals, newspapers, magazine articles, and web pages. In these cases, these data do not stand alone as a distinct element, but instead are part of the larger work.

When searching for data in books and articles and on web pages, terms such as statistics or data may or may not be useful search terms. That’s because many writers don’t use those terms in their scholarly writing. They tend to use the words findings or results when discussing data that could be useful to you. In addition, statistics is a separate discipline, and using that term will turn up journals in that area, which, more than likely, won’t be helpful to you. So, use the search terms data and statistics with caution, especially when searching library catalogs.

Even without using those search terms, many scholarly sources you turn up are likely to contain data. Once you find potential sources, skim them for tables, graphs, or charts. These items are displays or illustrations of data gathered by researchers.  However, sometimes data and interpretations are solely in the body of the narrative text and may be included in sections called “Results” or “Findings.”

Depending on your research question, you may need to gather data from multiple sources to get everything you need to answer your research question and make your argument for it.

For instance, in our example related to foodbanks above, we suggested where you could find statistics about the number of people who get food from American foodbanks. But with that research question (“Why is there a gap in the number of people who qualify for food from foodbanks and the number of people who use foodbanks?”), you would also need to find out from another source how many people qualify for foodbanks based on their income and compare that number with how many people actually use foodbanks.

Finding Data, Data Depositories, and Directories

Sometimes the numeric research data you need may not be in the articles, books, and web sites that you’ve found. But that doesn’t mean that it hasn’t been collected and packaged in a useable format. Governments and research institutions often publish data they have collected in discipline-specific data depositories that make data available online.

The United Nations and just about every country provide information as numeric data available online. Free and accessible data like this is called open data. The U.S. federal government, all states, and many local governments provide open data.

Other data are available through vendors who publish the data collected by researchers.

Evaluating Data as Sources

Evaluating data for relevance and credibility is just as important as evaluating any other source. Another thing that is the same with data is that there is never a 100% perfect source. So, you’ll have to make educated guesses (inferences) about whether the data are good enough for your purpose. We discuss how to do this in section 2.4.

Critical thinking as you evaluate sources is something your professors will expect. But you’ll benefit in other ways, too, because you’ll be practicing a skill necessary for the rest of your life, both in the workplace and in your personal life. It’s those skills that will keep you from being duped by fake news and taken advantage of by posts that are ignorant or, sometimes, simply scams.

To evaluate data, you’ll need to find out how it was collected. If the data are in another source, such as a book, web page, newspaper, magazine, or research journal article, evaluate that source in the usual way (see 2.4). If the book, newspaper, magazine, or web page got the data from somewhere else, do the same evaluation of the source from which the book or article got the data. The article, book, or web page should cite where the data came from. If it doesn’t, then that is a mark against using that data.[4]

In addition, if the data are in a research journal article, read the entire article, including the section called Methodology, which tells how the data were collected. Then determine the data’s relevance to your research question by considering such questions as:

  • Were the data collected recently enough?
  • Is the data cross-sectional (based on information from people at any one time) or longitudinal (based on information from the same people over time)? If one is more appropriate for your research question than the other, is there information that you can still logically infer from this data?
  • Were the types of people from whom the data were collected the same type of people your research question addresses? The more representative the study’s sample is of the group your research question addresses, the more confident you can be in using the data to make your argument in your final product.
  • Was the data analysis done at the right level for your research question? For instance, it may have been done at the individual, family, business, state, or zip code level. But if that doesn’t relate to your research question, can you still logically make inferences that will help your argument? Here’s an example: Imagine that your research question asks whether participation in high school sports in Columbus City Schools is positively associated with enrolling in college. But the data you are evaluating is analyzed at the state level. So you have data about the whole state of Ohio’s schools and not Columbus in particular. In this case, ask yourself whether there is still any inference you can make from the data.

To evaluate the credibility of the data in a research journal article you have already read, take the steps recommended in section 2.4, plus consider these questions:

  • Is the article in a peer reviewed journal? (Look at the journal’s instructions for authors, which are often located on the journal’s website, to see if it talks about peers reviewing the article and asking for changes [revisions] before publishing.) If it is a peer reviewed journal, consider that a plus for the article’s credibility. Being peer reviewed doesn’t mean it’s perfect; just more likely to be credible.
  • Do the authors discuss causation or correlation? Be wary of claims of causation; it is very difficult to determine a causal effect. While research studies often find relationships (correlation) between various variables in the data, this does not equal causation. For instance, let’s return to our example above: If the study of Ohio high schools students’ sports participation showed a positive correlation between sports participation and college enrollment, the researcher cannot say that participation caused college enrollment. If it were designed to show cause and effect, the study would not have resulted in a correlation. Instead, it would have had to have been designed as an experiment or quasi-experiment, used different statistical analyses, and would have supported or not supported its hypotheses.

Citing Data

Data is not copyrightable, but the expression of data is. So as with any other information source, you should cite any data you use from a source, whether it appeared in an article or you downloaded the data from a repository on the Web.

Unfortunately, data citation standards do not exist in many disciplines Current workarounds include:

  • Citing a “data paper,” where available.
  • Citing a journal article that describes the dataset.
  • Citing a book that includes the data.

Examples: Citing Data

Data from a research database:

  • APA: Department of Agriculture (USDA) (2008). “Crops Harvested”, Crop Production [data file]. Data Planet, (09/15/2009).
  • MLA: “Crops Harvested”, Department of Agriculture (USDA) [data file] (2008). Data Planet, (09/15/2009).

Data from a file found on the open Web:

  • APA: Center for Health Statistics, Washington State Department of Health. (2012, November). Mortality Table D1. Age-Adjusted Rates for Leading Causes of Cancer for Residents, 2002-2011. [Microsoft Excel file]. Washington State Department of Health. Retrieved from http://www.doh.wa.gov/
  • MLA: Center for Health Statistics, Washington State Department of Health. Mortality Table D1. Age-Adjusted Rates for Leading Causes of Cancer for Residents, 2002-2011. Washington State Department of Health, Nov. 2012. Microsoft Excel file. Retrieved from http://www.doh.wa.gov/Citing the dataset as a website, where possible.

Proper Use of Data

Once you have your data, you can examine them and make an interpretation. Sometimes, you can do so easily. But not always.

Many people have a tendency to look for data to prove their hypothesis or idea, as opposed to really answering their research questions. However, you may find that the opposite happens: the data may actually disprove your hypothesis. You should never manipulate data so that it gives credence to your desired outcome. While it may not be the answer you wanted to find, it is the answer that exists. You may, of course, look for other sources of data – perhaps there are multiple sources of data for the same topic with differing results. Inconclusive or conflicting findings do happen and can be the answer. Conflicting results on the same topic are common. This is the reality of research because, after all, the questions researchers are studying are complicated. When you have conflicting results you can’t just ignore the differences—you’ll have to do your best to explain why the differences occurred.

People as Sources

People don’t just create the sources we use. They are actually sources them-selves. Most of us use people as sources all the time in our private lives, such when we ask a friend for a restaurant recommendation or ask whether a movie is   worth watching. But you probably aren’t using people as sources very often in your assignments–unless you are a journalism major, of course.

In fact, research indicates that employers such as Battelle, Nationwide Insurance, Microsoft, the FBI, the Smithsonian, the Port of Los Angeles, SS&G Financial Services, and Marriott International have been dissatisfied with their new hires’ inability to gather information by talking with real people. They’ve found new hires unwilling or unprepared to ask the experienced employee down the hall or the expert across town for information to solve a problem. For instance, the study linked above quotes one employer as saying this about new hires:

Here’s something we’re targeting in interviews now—the big thing is they believe the computer is their workspace, so basic interactions between people are lost. They won’t get up and walk  over and ask someone a question. They are less comfortable and have some lack of willingness to use people as sources and also have a lack of awareness that people are a valid source of information…[5]

So getting some experience using people as sources is likely to help you not just with a current research assignment but with your work in the future.

Important: Who’s an “Expert”?

Experts aren’t only researchers with Ph.Ds doing academic work. The question when trying to decide who can be a source is really always, who can speak with authority about any part of the subject? And the answer to that question is always contextual, a kind of “it depends.”

People can speak with authority for different reasons. According to the framework for information literacy, they can have subject expertise (say, having done scholarship in the field), societal position (maybe a public office or another relevant work title), or special experience (say, living or working in a particular situation of interest or having participated in a historical event).

For instance, people who have had firsthand experience living or working with a situation (say, a survivor of school shooting if your topic is on that subject) you are studying can have a unique perspective unavailable elsewhere. And it’s that up-close, firsthand view of the situation that gives them the authority that you and your audience respond to.

Of course, such sources have to be evaluated just like any other. Could they be biased? Like any source, yes. We just have to keep that possible bias in mind as we use the information from such a source. That’s part of exercising the critical thinking that research assignments are famous for producing.

Potentially biased or not, sometimes a source’s firsthand experience can’t be beat. And recognizing what they offer can help us open up to diverse ideas and worldviews that we would otherwise miss. Don’t be surprised if this kind of source takes you off in completely new directions with your assignment, ones that turn out to be much more interesting than those you were following before. For many researchers, finding sources that open up a topic like that is one of the most rewarding—and fun—things about doing research.

Some Examples of People as Sources

Research Question Potential Person as Source Potential Person as Source
How are tools originally developed for medicine, geology, and manufacturing used to explore paintings and sculptures? An art conservator who uses those tools that you read about in the newspaper or other source The person who invented one of the tools on the floor of the factory where he works
Why do most people who qualify for food at foodbanks not ask for food? A local food bank director A person (perhaps a fellow student) who qualifies but does not ask for food at a food bank
How and why do city and county governments brand themselves? An official in such a city or county who has been involved in branding decisions The director of a company that designs branding for cities and counties

You can interview a person as a source on the phone, in email, by Skype, or face-to-face. You’ll need to:

  • Pay attention when reading other sources so you can identify whom to contact and know what they could have to offer.
  • Prepare by learning enough about your topic so you can ask appropriate questions, know what your expert has done in relation to that topic so you don’t seem ignorant of their contribution, and know how to contact them. You might also want to do a practice interview with a friend.
  • Contact your source to see if they are willing to talk with you and when that would be convenient. Then follow through.

Use good interview techniques, such as trying to put them at ease, using active listening techniques to encourage them to talk, asking follow up questions, and thanking them at the end of the interview.

Citing People as Sources

Like other sources, people should be cited in your research final product, depending on the citation style you’re using. For instance, in APA style, interviews, e-mail, and other personal communication (i.e. non-published interviews) should not appear in the reference list but should be in your main text only like this: (A. Authorslastname, personal communication, July 29, 2018).

Media Attributions

  • Lindsey MacCallum and Teaching & Learning Ohio State University Libraries

  1. 2.3 (except where otherwise noted) was borrowed with minor edits and additions from Choosing & Using Sources: A Guide to Academic Research, 1st Canadian Edition by Lindsey MacCallum and Teaching & Learning Ohio State University Libraries which is licensed under a Creative Commons Attribution 4.0 International License
  2. Raff, J. (2013, Aug. 13). How to read and understand a scientific paper: A guide for non-scientists. Violent metaphors: Thoughts from the intersection of science, pseudoscience, and conflict. Received June 11, 2022, from https://violentmetaphors.com/2013/08/25/how-to-read-and-understand-a-scientific-paper-2/
  3. Erway, Ricky. 2013. Starting the Conversation: University-wide Research Data Management Policy. Dublin, Ohio: OCLC Research. http://www.oclc.org/content/dam/research/publications/library/2013/2013-08.pdf
  4. While the data in a research journal article are often the work of the authors of the article, you’ll want to be sure they provide information about how they collected the data.
  5. The Workplace Report from Project Information Literacy is licensed under a Creative Commons (CC) license of “CC BY-NCSA 4.0.”

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