Abstract: An indexing system for a reference book which is printed on the edge of the pages opposite to the binding so as to be visual when the book is closed; the system including primary, secondary, and further subdivided portions of the book identified by large letters, succeedingly smaller letters, and color coded marks to represent respective portions of the book where the contents relate to words having a first letter corresponding to the large letters, a second letter corresponding to the next smaller letter, and a third and succeeding letters represented by still smaller letters or a color coded mark.