Literature Review

Primary vs. Secondary Research Sources: The Impact on Your Paper

It’s important that the claims you make in your research paper are backed up by sound evidence from reliable sources. If you fail to do so, your article risks not standing up to an analysis from your journal’s peer reviewers.

What are ‘reliable’ research sources? And does the APA style allow you to use all kind of sources for your research paper?

Is it okay, for example, to cite blogs in your literature review? Or discussion sections? Or sources published over 20 years ago?

You can indeed. Go ahead and cite any source in your reference list, but on one condition: your readers must be able to find your source through the information you have given in your reference list.

Still, just because you can cite any retrievable source doesn’t mean you should. Your sources need to be 1. reliable and, preferably, 2. primary sources. Primary sources offer well-researched information. Sources that your readers cannot retrieve (unrecorded conversations, in particular) can still be cited as ‘personal communication’.

What, then, does APA mean with ‘reliable’ sources?

I don’t think you’ll be surprised if I tell you that the following two main indicators will throw in their weight:

  • the expertise of the author(s) you are citing
  • the reputation of the journal you are citing from

If the author you are citing is a researcher and has previously published in a peer-reviewed journal: relax! If that journal is also listed as a “scholarly” publication in the SCI, SSCI, SJR or, at the very least, the ISSN databank, go ahead and do cite that author.

If, however, you intend to cite from a website made by an unidentified person, such source is less likely to be reliable. You really should refrain from adding it to your reference list. Unless you have a good reason to do so, of course.

Such reason could be that you plan to discuss the questionable standards of online material. Alternatively, you might also want to research the information you found on that website, but then by using more reliable sources – and with the latter I mean sources not from anonymous websites.

Don’t get me wrong: APA rules do allow you to include information published online without a person’s name, and such source can prove reliable. But what APA usually refers to are scientific organizations (like APA itself) that publish online information. Also, researchers or research organizations might publish blogs (like this one) or YouTube videos that are worth citing.

So: take enough time to evaluate each source for reliability before taking a decision on whether or not to include it in your paper!



A primary source gives firsthand information, like:

  • the findings of a survey
  • data from an experiment
  • a book or website which describes a theory or technique developed by the author himself

A secondary source gives secondhand information, like:

  • a Wikipedia article
  • textbook article
  • encyclopedia entry

APA guidelines prescribe: try using as many primary sources as possible for your paper. And that’s good advice! In doing so,  there’s no need to check the accuracy and completeness of the information you are citing in your paper.

For secondary sources, verify that the information is reliable enough to add to your literature review. It’s like repeating information from someone who only heard about the events but who did not witness them personally.

So you’ve guessed it: most of the sources you use in your research paper should be primary. You save time and effort. And you’ll even please those peer reviewers who follow APA rules to the (very) letter.

In case you’re not sure whether a document is of  primary or secondary origin, there’s a solution. Ask yourself:

Did the authors of this source discover the data themselves (= primary source), or are they reporting on what someone else found (= secondary source)?

At times the line between primary and secondary sources are indeed blurry and you have to judge a number of your sources individually.

Some types of sources are typically considered as primary:

  • articles from peer-reviewed journals (‘scholarly’ journals, in other words)
  • chapters from a book
  • newspaper articles (but no tabloids)
  • articles from reputable magazines (Times, Forbes, etc.)
  • reports from governmental and scientific organizations
  • PhD theses (published)

And yet, secondary sources do have two major advantages:

  • They can guide you to primary sources, in particular those that you might otherwise not have noticed.
  • They make for considerably ‘lighter’ reading. So by reading ‘for fun’ (secondary sources), you might be made aware of an interesting source of information for your research paper which you may then use – provided you do the extra effort of verifying the correctness of the information in the secondary source.

I’d like to stress again that you really do need to check the accurateness of a secondary source before including its information in your paper.

You might, in the worst case, hear from another colleague that the truth is opposite to what you wrote in your paper.

So, even when secondary sources might seem highly credible (e.g., material in a handbook by a well-known publisher), being thorough and finding the primary source shows that you deserve to be called a researcher.



APA guidelines recommend using ‘up-to-date’ primary sources. But exactly how recent should your primary citations be? This depends on your field of study.

Literary sources, for example, may date back further than, let’s say, social science sources. Literary research remains relevant longer than studies in psychology or linguistics. Linguistics, in turn, will stay relevant longer than research in mathematics or physics. Even within physics, some information will remain relevant for a long time, while other data will become outdated much faster. If you were to do a psychological analysis of multi-tasking skills, for example, you’d probably not want to look at research before the introduction of social media some 20 years ago.

Still, APA does not provide a clear year-cutoff in which your sources should have been published. You will have to make a decision on whether or not to use older sources on a case-by-case basis, depending on the importance you attach to the information you wish to cite.

I hope this post has helped you in better understanding the difference between primary and secondary research sources, and how they can best be used in writing a solid research paper.