What is firmly established cannot be uprooted. What is firmly grasped cannot slip away.Lao Tsu*
Many ideas that you get are based on sources that in turn make a reference to another source. You could always find that original source and read it since there are a lot of misquoted material out there. Anyone ever playing telephone knows how easy for a message to be gradually altered along the way. However, from time to time finding the original source can be hard or close to impossible. Especially when it comes to very old publications that haven’t been reprinted recently.
Here is a page with resources and material to use. If you are looking for how to use and cite figures, screenshots, code etc. please refer to the following documents: How to use and cite figures from other sources, How to cite screenshots, References to secondary sources and review articles, Writing references to personal communication, Writing references to programming code, Citing content created by generative AI (ChatGPT), and How to visualize your data in an understandable way.
Reference to a secondary source
These guidelines are based on the following sources:
A secondary source, is a source that is cited or quoted in another source. The most common example is a article that cites another article. In the example below
Buttle (2009) and
Langlois (1992) are both cited by
Mejtoft (2010). In other words, none of this information is derived by
Mejtoft (2010) but are results by the original authors and the sources cited. Hence, it is
Buttle (2009) and
Langlois (1992) that should be read and cited in your work if you want to write about the concept of having good customer relations.
Screenshot from Mejtoft (2010)
In scientific writing, and generally in most writings, it is important to actually read the original sources before using them as a reference. This is (most often) the only way that you can make a reference to the source in your writings.
Tip of the day! Do not make references to secondary sources due to laziness!
However, in some cases it is not possible to get hold of the original source. It might be out of print or non-accessible. A 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 e.g., a peer-reviewed scientific publication. 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. Hence, both the paper you have read and the original source should be quoted in-text and the secondary source should be added to the reference list. You should, however, never base core/important parts of your writings on secondary sources.
Below are some examples on how to write a text referring to a secondary source.
<Original Author(s)> argue that .... (as cited in <Secondary Author(s)>) e.g. Simpson (1997, as cited in Mejtoft, 2008) argues that facts are meaningless. There are indications that facts are meaningless (Simpson, 1997, as cited in Mejtoft, 2008) or Simpson (as cited in ) argues that facts are meaningless. There are indications that facts are meaningless (Simpson as cited in )
The reference that is put in the reference list is, in this case, the secondary source (i.e., only the source that you have actually read!). In the example above it is the secondary source (Mejtoft, 2008) that should be a post in the reference list. The original source (Simpson, 1997) should not be put into the reference list since it has not ben read or used.
Reference to a review article
Often, it is possible to find very nice review articles (i.e., articles that compile data from previous published research to for example give an overview). In other words, the actual data is (usually) not new, but there might be new analysis, discussions, or conclusions in the review article based on the compiled data.
When referencing a review article it is important to decide whether the review article should be referenced or if a reference should be done to one (or several) of the articles that are included in the review. If you are making a reference to a specific conclusion from one of more of the included articles, then the reference should be given to the specific article(s) (that is included in the review) where the author(s) have made this specific conclusion. However, the final data/analysis/discussion/conclusion in a review article might also be 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. If the conclusion of the compiled data is the source you are referencing, the reference should be given to the review article as an ordinary reference.
Below is an honest way of writing the reference that also indicate that this is a review article:
In a review by Mejtoft (2007) ... In the 50 articles reviewed by Mejtoft (2007) ... or In a review by Mejtoft  ... In the 50 articles reviewed by Mejtoft  ...
If you are looking for information on how to write references to personal communication: Reference to personal communication
*Quote from Tao Te Ching (Tsu, 600BC/1997, ch. 54).
Tsu, L. (1998). Tao Te Ching (G-F. Feng & J. English, Trans.). Vintage Books. (Original work published around 600 BC).
(First published by Thomas Mejtoft: 2019-03-19; Revised: 2021-04-20; Last updated: 2023-08-21)