These books can tell you more about the cultural, historical, and political forces that shaped cinematic productions in the 1960s & 1970s.
Hollywood Left and Right: How Movie Stars Shaped American Politics by Reference works such as specialized encyclopedias, dictionaries, and handbooks can provide
International Dictionary of Films and Filmmakers (e-book)
Encyclopedia of Film Themes, Settings and Series by 
The Oxford History of World CinemaSearch multiple reference sources at once.
