Main headings are the primary subject headings in an index that is organized alphabetically by subject. They are also the organizing structure for that index. Main headings correspond to the primary concept category terms in your concept table, although the main heading term may not be identical to the one you used. Most of the time, these terms appear in bold face type.
Indexes organized by abstract number do not generally use main headings. They usually have a larger number of subject headings which are listed in alphabetical order in a subject index. Sometimes the subject index will have an hierarchical structure and you will find subdivisions following a main heading.
Use terms from your primary concept category when you start your search of a print index. If your topic is an important event, person, or idea, the name of that event, person, or idea will generally be the main heading or primary subject heading term.
Thesis statement:
Your primary concept is the 1973 Wounded Knee confrontation. This is a very specific event. As a result, Readers Guide to Periodical Literature used it as a main heading.
Under this heading: Wounded Knee, S.D. you will find a number of references including the following:
