Examples of Controlled Vocabulary Systems

1) LC Subject Headings (assigned to books in CONSORT, hyperlinked and browsable)

2) The Thesaurus of the American Psychological Association (hyperlinked and browsable; use it when searching PsychINFO for articles)

3) Subject Terms in Humanities Abstracts (hyperlinked and browsable)

4) HTML Keyword Metatags in web page source code (not hyperlinked or browsable; noticed only by a small number of search engines--more or less inconsequential for a searcher)