A speaker who wants to include the words of Winston Churchill in a speech should search in which of the following?

Choosing Bartlett's Familiar Quotations is the most appropriate for a speaker looking to include Winston Churchill's words in a speech because this reference book specifically compiles notable quotations from a wide variety of authors and public figures. It is designed to help users find quotes on diverse topics, making it ideal for speakers seeking to enhance their speeches with impactful and recognized remarks.

In contrast, while the International Who's Who may offer biographical details about Churchill, it does not focus on quotations. Encyclopedia Britannica provides general information and context about Churchill's life and work but lacks a dedicated compilation of quotes. The ProQuest Research Library is a database for academic research, which, although it might have articles about Churchill, would require more effort and time to search for specific quotes compared to the straightforward and targeted approach offered by Bartlett's. Thus, for quick and effective access to well-known quotations, Bartlett's Familiar Quotations stands out as the best resource.