See the website of the CEU Center for Academic Writing, particularly the following:
It's important to cite sources you used in your research for several reasons:
You must cite:
When in doubt, be safe and cite your source!
Citing a source means that you show, within the body of your text, that you took words, ideas, figures, images, etc. from another place.
Citations are a short way to uniquely identify a published work (e.g. book, article, chapter, web site). They are found in bibliographies and reference lists and are also collected in article and book databases.
Citations consist of standard elements, and contain all the information necessary to identify and track down publications, including:
Citations may look different, depending on what is being cited and which style was used to create them. Choose an appropriate style guide for your needs. Here is an example of an article citation using three different citation styles. Notice the common elements as mentioned above:
Authors - Roberto Stefan Foa and Yascha Mounk
Article Title - The Signs of Deconsolidation.
Source Title - Journal of Democracy
Volume and issue - Vol 28, issue 1
Publication Date - 2017
Page numbers - 5-15
American Psychological Association (APA) style:
Foa, R. S., & Mounk, Y. (2017). The Signs of Deconsolidation. Journal of Democracy, 28(1), 5–15.
Chicago Manual of Style:
Foa, Roberto Stefan, and Yascha Mounk. “The Signs of Deconsolidation.” Journal of Democracy 28, no. 1 (January 10, 2017): 5–15.
OSCOLA (Oxford University Standard for Citation of Legal Authorities):
Foa RS and Mounk Y, ‘The Signs of Deconsolidation’ (2017) 28 Journal of Democracy 5