<P> The back cover often contains biographical matter about the author or editor, and quotes from other sources praising the book . It may also contain a summary or description of the book </P> <P> Books are classified under two categories according to the physical nature of their binding . The designation hardcover (or hardback) refers to books with stiff covers, as opposed to flexible ones . The binding of a hardcover book usually includes boards (often made of paperboard) covered in cloth, leather, or other materials . The binding is usually sewn to the pages using string stitching . </P> <P> A less expensive binding method is that used for paperback books (sometimes called softback or softcover). Most paperbacks are bound with paper or light cardboard, though other materials (such as plastic) are used . The covers are flexible and usually bound to the pages using glue (perfect binding). Some small paperback books are sub-classified as pocketbooks . These paperbacks are smaller than usual - small enough to barely fit into a pocket (especially the back pocket of one's trousers). However, this capacity to fit into a pocket diminishes with increasing number of pages and increasing thickness of the book . Such a book may still be designated as a pocketbook . </P> <P> Some books such as Bibles or dictionaries may have a thumb index to help find material quickly . Gold leaf may also be applied to the edges of the pages, so that when closed, the side, top, and bottom of the book have a golden color . On some books, a design may be printed on the edges, or marbling or a simple colour applied . Some artist's books go even further, by using fore - edge painting . Pop - up elements and fold - out pages may be used to add dimensions to the page in different ways . Children's books commonly incorporate a wide array of design features built into the fabric of the book . Some books for preschoolers include textured fabric, plastic on other materials . Die - cut techniques in the work of Eric Carle are one example . Clear or reflective surfaces, flaps, textiles and scratch - and - sniff are other possible features . </P>

Order the following parts of a leaf from top to bottom