When citing you acknowledge the work of others for the sources you have used in your academic thesis or publication. Besides giving authors of these sources credit for their work, citing enables your readers to find your information sources. Also, citing sources can help to support your ideas and arguments and thereby helps to improve the credibility and reliability of your work.

The acknowledgements of the used sources in the body of your texts are called citations, providing brief details of each source in an author-date or numeric style. At the end of your document, you must give full details of the sources you used in a reference list or bibliography.

Citing from a secondary source

Before citing to any source you should always try to read the original work, known as the primary source. If, however, you are forced to cite a secondary source because you cannot consult the original work, you have to cite the original work as contained in the secondary source.

This means for the in-text citation that you include both the original and the secondary source (e.g. Habermehl, 1985 as cited in Kersten, 1987). In your reference list you should (at least) provide the details of the secondary source (the source you read). In this example: the details of Kersten, 1987. Sometimes (particularly in numeric styles) you may also include the secondary source in your reference list.


An essential legal reason to acknowledge your sources is to avoid plagiarism. Plagiarism is considered a serious academic offence. It means that you present others’ work as yours own without clear acknowledgment of the source of information you used. To avoid plagiarism in your texts or presentations you must cite any ideas or data that are not your own. Besides others’ texts, this includes statistics, tables, figures, pictures, illustrations, etc. The same rules apply for both printed and electronic sources.

There are three different ways of citing: quoting, paraphrasing and summarising. Each asks for correct citation to prevent plagiarism.


If you directly copy the words of another author (word for word), you are quoting a source. You should use direct quotations sparingly, and only when you have a very good reason to use an author’s exact words. Short direct quotations must be put within quotations marks. In case of quotations of considerable length (i.e. block quotations) you do not use quotation marks. The format for these block quotations may vary for different styles, but generally they need to be separated from the rest of your text, usually intended and in smaller font size.

For direct quotations, within the citation the page number(s) of the quoting text must be included. Be sure that you are very accurate in your quotation. If you leave out part of a quotation, you must use an ellipsis: three or four dots with spaces between and around them, thus . . . or . . . . The number of dots depends on the part of the sentence and the number of sentences you leave out, and the citation style. If you need to add some words or comment within a quotation, indicate your addition by using square brackets, [ ].


Using your own words to present the information and ideas of an author, is called paraphrasing. This is generally preferable to direct quotation. If you are restating words or ideas, do not alter the meaning or provide your interpretation or opinion. Be sure you are not just rearranging or replacing words, or composing a kind of “patchwork paraphrase” by rearranging original words and your own words into a new pattern, without putting original words in quotation marks. When paraphrasing, page numbers are not essential. However, if the cited work is long it might be useful to the reader to locate the relevant information.


Putting the main points of another author into your own words, is called summarising. Also when you are summarising, cite the source and be careful not to alter the meaning or to provide interpretations and opinions. When summarising, page numbers are not essential but may be included to help readers to locate the relevant information.

Citation styles

There exist a lot of different author-date or numeric styles for in-text citations and reference lists. Which style you have to apply depends of several factors, such as the type of document you are writing (e.g. thesis or journal article), you subject discipline, institutional guidelines and regulations, etc.

Wageningen University & Research has no general guidelines or regulations on citation styles for theses, papers or reports. You can ask your teacher/supervisor which style you should use. If there is no preference, you can use any style you like. Just bear in mind that it is very important to be accurate and consistent. Do not use different citation styles in one work.

Several organisations provide discipline-specific citation styles. Some commonly used citation styles include Harvard style (also called author-date or name-date style) for several different disciplines, APA (American Psychological Association) style for Psychology, the CSE (Council of Science Editors Style) style for Biology, numeric style (also called numbered list or Vancouver style) for Biomedical Sciences, and NLM (National Library of Medicine) style for Medicine. Consult the citation guides to find more citation styles and details on how to cite your sources, how to compose your reference list and other details. An alternative is to take a renowned journal in your field, and find out how the different types of sources are cited in its articles and how reference lists are organized (including punctuation, font etc.).