Primary and secondary sources for your thesis

In your thesis, you will use various sources. Here, we distinguish between primary and secondary sources. In other words: original sources and sources that refer to another original source. What exactly does this mean? Can you use both primary and secondary sources for your thesis? How can you be sure that a source is reliable? We explain all of this to you using examples.

Primary sources are original sources. This means that you look at a particular study, situation, or experience through the eyes of the researcher, an expert by experience, or a witness. This is the case, for example, in research articles. The researcher then elaborates on the research they conducted and draws conclusions based on it. 

Secondary sources are those that discuss research, findings, experiences, or creations of others. Within secondary sources, a primary source is interpreted or analysed. These sources are further removed from the topic that is being studied. For example, they refer to research conducted by others and give a brief summary of it. Examples of secondary sources are literature reviews (in which various sources are discussed) or a documentary.

In particular, we recommend using primary sources for your thesis. These are the most reliable. This is because you then base your stance on the original source and the researcher's own interpretation of it. If you use a secondary source, there is a chance that you will use an incorrect interpretation of the primary source for your thesis. 

Examples primary source

Primary sources involve reading direct results, interpretations, or reports rather than information about them. Primary sources are not interpreted or summarised by other people, so you are as close to the source as possible. 

These are some examples of primary sources:

• A scientific article on a research project conducted in-house;

• statistical results;

• surveys and interviews;

• legal documents;

• eyewitness reports;

• photos and videos depicting a situation or event;

• audio recordings of a conversation;

• a painting;

• a film;

• a song;

• an autobiography;

• a patent.

Example: primary source 1

Suppose you want to research a particular police interrogation. Your best bet then is to rely on the primary source. In this case, that is the audio recording of the interview or a verbatim transcription of it. An eyewitness account of an event is also a primary source. These sources are more reliable than if you delve into someone else's study of this particular interrogation.

Example: primary source 2

Another example of a primary source is an empirical study you conduct yourself. For example, you conduct research on news consumption among young people aged 15-18 at a secondary school in The Hague. For this, you conduct surveys among the target group, analyse the results, and describe them in a research report. 

Your research is then a primary source because you as the researcher share and interpret the original data. This is not done by someone who is not involved in the research.

Secondary sources are (collections of) analyses or interpretations of primary sources. As a result, secondary sources are further removed from the primary source. 

Examples of secondary sources are:

• Literature studies;

• review articles;

• editorials;

• textbooks or volumes discussing studies;

• documentaries;

• news reports (which do not include eyewitness accounts);

• a catalogue of art;

• film reviews;

• a book someone else has written in which the writer has created a portrait of a particular person;

• blog articles about a particular study.

Example: secondary source 1

You are curious about others' interpretations of the police interrogation you are investigating. Online, you come across a documentary by someone interpreting this interrogation. You also come across an academic publication by someone who compiles various findings about this interrogation. Both are examples of secondary sources. 

Example: secondary source 2

You want to research news consumption among young people aged 15-18. Within your plan of action, it is not feasible to conduct your own surveys or interviews. Therefore, you decide to do literature research. You collect a large number of articles on the subject, start interpreting them and compare the results. Using this information, you write your thesis. 

In this case, your thesis is a secondary source because you rely on interpretations, not your own results.

Primary sources are often preferred, but that does not mean that secondary sources are not useful at all. The use of secondary sources can still be appropriate for your thesis. For instance, there are extensive literature reviews that highlight a large number of previous studies. Such a literature review can certainly be relevant to your thesis. 

Most students use primary as well as secondary sources for their thesis. This is possible as long as you are aware of possible bias in secondary sources. 

Does a secondary source cite a particular primary source? If so, it is always good to look into the primary source yourself. That way you can be sure that you are interpreting this source correctly. Have you been able to find and look into the primary source? Then refer to that primary source in the text as well. Is that primary source not accessible? Then you can refer to its interpretation using the secondary source (and cite the secondary source in your bibliography). Do make it clear that this is an interpretation.

Whether it is a primary or secondary source, you must use the correct source citation. Each source used should be given a place in the bibliography and the running text, and formatted according to certain guidelines set by your study programme or supervisor. 

Most studies use the APA style for this purpose. Within legal studies, the Guideline for Legal Authors is the common referencing style. 

Proper citation of sources is rather tricky. Doing this correctly prevents you from (accidentally) committing plagiarism. Are you unsure of whether you have referenced your sources correctly in your thesis? Get your sources checked by one of the AthenaCheck editors. They will carefully check each source for you and adjust your sources where necessary starting from as little as € 2 per source!