My favorite Twain reference book is EVERYONE'S MARK TWAIN, compiled by Caroline Thomas Harnsberger (South Brunswick and New York: A. S. Barnes [c1948 and 1972] 703p.), which consists of excepts from Twain's writings (with precise references to title, chapter, and page)arranged alphabetically by subject. A bibliography of works by and about Twain is included. Clara Clemens wrote the Foreword and concluded by saying:"I cordially commend...[this reference book] not only to the attention of the lovers of my father's writings, but to the reader who has not yet become acquainted with Mark Twain." Ask a library near you to locate a copy for you to use, or check http://www.bookfinder.com if you want to purchase a used copy. ET