Book reference is a term used to describe a variety of resources that can be used to find information about books. The three crossword solutions for this term are INDEX, ATLAS, and Roget. An INDEX is an alphabetical list of topics found in a book or other publication, which can be used to quickly locate specific information. An ATLAS is a collection of maps and geographical information, which can be used to locate places mentioned in a book. Finally, Roget is a reference book containing a thesaurus of words and phrases, which can be used to find synonyms and antonyms for words used in a book.