Search for the origin of the knowledge and, if possible, quote from the original texts. A distinction is made between sources that are citable and sources that are worth citing.
Citable sources
Citable are all sources that are permanently and publicly accessible.
Lecture notes are generally not considered scientific publications, as they are not publicly accessible. They are therefore not citable. The same applies to internal documents from companies that are subject to confidentiality.
Worth citing
Worth citing for scientific statements are sources that
- were written by authors who themselves have conducted scientific work and are currently relevant to the topic, i.e. not necessarily “new” but “relevant for today”,
- were published by a reputable institution (academic publisher, university, research institute) and, as a rule, have been peer-reviewed by other scholars.
Not worth citing are therefore daily newspapers and tabloid magazines, user manuals, operating instructions, company brochures, any other internal company documents, as well as conversations.
Sources that are not worth citing may not be used as evidence for a fact or to justify a course of action. A citation based on such a source is therefore inadmissible.
In some cases, however, using a source that is not worth citing can be helpful to illustrate something (e.g. images from the internet) or unavoidable to explain a technical background (e.g. manuals).
In these cases, always create a PDF document for each of these sources (scan or print as PDF) and submit these documents on the digital storage medium when handing in your thesis in a dedicated folder. This also applies to user manuals or similar documents. You should copy these in full to the CD.
Frequently asked questions
How do I find the right sources?
Search for the origin of the knowledge and, if possible, quote from the original texts.
Which sources are not worth citing?
Not worth citing are e.g. daily newspapers and tabloid magazines, user manuals, operating instructions, company brochures, any other internal company documents, as well as conversations.
What should I keep in mind when working with sources that are not worth citing?
In some cases, sources not worth citing can be helpful to illustrate something or to explain a technical background. Be sure to correctly identify the use of such sources and list them in the bibliography.
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This article was published in August 2025 and last updated in November 2024.