"Within the limits of time, budget, sanity, and common sense, you should try to read as much as possible about the subject. Your aim is simple: within a very short time, you want to become, if not an expert in the field, at least a person with a superior knowledge of the subject. Print and web research can involve scanning databases, checking bibliographies and print sources, and reading books, papers, magazines, trade journals, articles, diaries, letters, and even congressional records and transcriptions of court trials...if you don’t understand the material, you won’t be able to say anything sensible about it in the film."
Rosenthal, Alan, and Ned Eckhardt. Writing, Directing, and Producing Documentary Films and Digital Videos. Vol. Fifth edition, Southern Illinois University Press, 2016.