Reference to secondary sources and review articles

Reference to a secondary source

A secondary source is a source that is cited or quoted in another source. In scientific writing, and generally in most writings, it is important to actually read the original source. This is the (most often) the only way that you can make a reference to the source in your writings.


However, in some cases it is not possible to get hold of the original source. It might be out of print or not accessible. The most common scenario is that you have read the content and understood the essence of the original source (that cannot be found) in a secondary source.

In this case, the most important thing is that the secondary source have a high credibility. It is important the the secondary source is of extremely high quality and should (most often) be a peer-reviews scientific publication. Do never base core/important parts of your writings on secondary sources. If you believe that the credibility of the secondary source is high enough it is possible to add a reference to the secondary source quoting the original source.

<Original Authors> argue that .... (as cited in <Secondary Authors>)


Simpson argues that facts are meaningless (as cited in Mejtoft, 2008)


Simpson argues that facts are meaningless (as cited in [23])

The reference that is put in the reference list is the secondary source, i.e. only the source that you have actually read! In the case above it is Mejtoft (2008) that is put into the reference list. The original source (Simpson) should not be put into the reference list.

Reference to a review article

In many cases it is possible to find very nice review articles (i.e. articles that compile data from previous published research to e.g. give an overview). The data/conclusions in a review article is (in most cases) to regard as a primary source. In other words, the author(s) of the review article have, e.g. compiled and made conclusions bases on many articles and (in some cases) their own results. The reference in this case should be as a ordinary reference, this is an honest way of writing the reference that also indicate that this is a review article:

In a review by Salo (2017) ...
In the 50 articles reviewed by Salo (2017) ...  


In a review by Salo [4] ...
In the 50 articles reviewed by Salo [4] ...  

(First published by Thomas Mejtoft: 2019-03-19; Last updated: 2021-02-10)