Help:References and page numbers
When citing sources in Wikipedia articles, the citation must clearly support the material as presented in the article, per the verifiability policy. It helps to give a page number or page range—or a section, chapter, or other division of the source—because then the reader does not have to carefully review the whole cited source to find the relevant supporting evidence, which promotes efficient source checking. This page shows examples of various ways to include a page number or page range in citations as well as various ways to cite the same source multiple times with different page numbers. It also summarizes ways to include other in-source locations.
The following examples use Citation Style 1 templates, but these are not required (see the section Inline citations in the guideline Citing sources for alternatives). For a basic introduction to citation templates, see Help:Referencing for beginners with citation templates.