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]
Special Words by Joyce Landorf Heatherley "Notes for When You Don't Know What to Say" Sample letters for all of those difficult and emotional times of life. Just be careful that you don't plagarize outright, you might get caught. There are over 200 letters organized by subject. [More Other Reference Books]
