A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

The requirements of citation - Situations requiring citations
General introduction to citation practices
Part II. Source Citation

To fulfill the requirements of citation, you need to know when to include a source citation in your paper and what information about the source to include.

15.2.1 Situations requiring citations

Chapter 7, particularly 7.9, discusses in depth when you should cite materials from other sources. Briefly, you should always provide a citation in the following situations:

when you quote exact words from a source (see also chapter 25 on quotations)

when you paraphrase ideas that are associated with a specific source, even if you don't quote exact words from it

when you use any idea, data, or method attributable to any source you consulted

As noted in 15.1, you may also use citations to point readers to sources that are relevant to a particular portion of your argument but not quoted or paraphrased. Such citations demonstrate that you are familiar with these sources, even if they present claims at odds with your own.