Another type publishing is educational books which are produced by special publishers or by educational of departments of trade publishers. These books are the textbooks used for instruction in colleges. The publishers sell some of their books directly to buyers in school They also distribute their books through college bookstores, Educational publishing is probably the most profitable area of book publishing. A great number of teachers and students are required to buy certain textbooks for their classes. Many publishers use the profits from this type of books publish trade books that may have uncertain sales prospects. Reference books are the last category of publishing. These include encyclopedias, dictionaries, almanacs, and similar books that contain information about a wide variety of topics. The material is organized so that the user can find facts quickly and easily. Many of these b enjoy large sales to libraries, where people go to look up information. Reference books are sold to individuals and families who want to have sources of information readily available. Many reference publishers use sales representatives who demonstrated and sell the books in the home Some reference publishers allow their clients to pay for the books in installments.