The International Thesaurus of Quotations by Eugene H. Ehrlich (Editor), Marshall Debruhl (Compiler) More than 16,000 quotations organized by subject, not author. With categories ranging from Ability to Zen, there are plenty to choose from (over 1000 categories). There is also an author listing in the back, just in case you need to look up quotes by author. [More Reference Quotation Books]
Merriam Webster's Biographical Dictionary by Merriam Webster (Publisher) Yet another biographical dictionary. This one is very general. There are no more than four or five sentences per person, but it usually is enough information to get an idea of what kind of person you are quoting. [More Other Reference Books]
