Those pages often use citation templates from Wikipedia. The templates categorized in this category were created by following some of the red links found on the Template:Citation page. The wikitext for that template, and its component templates, was copied from Wikipedia: Template:Citation, etc.. There are many templates that make that main template work. This link pulls them up.
Some Wikipedia info:
Pages in category "Citation-related templates"
The following 19 pages are in this category, out of 19 total.