Most books have a 10-digit ISBN (International Standard Book Number) which is a unique identifier for a particular publication. The ISBN for a hardcover book will be different from that for the paperback of the same title. The first edition of a book will have a different ISBN from later editions. You can usually find the ISBN on the verso (back) of the title page.
Other Standard Numbers
Magazines and journals also have a standard number, the 8-digit ISSN. Items cataloged by OCLC have an OCLC number.
Find Books Using Standard Numbers
Most books and journals have standard numbers such as an ISBN for a book or an ISSN for a journal. If you know the it, searching by standard number is often a quick way to find the specific book you need.
Example: a Title (Exact Phrase) search for the book Child Psychology finds 44 entries; a Standard No. search for the book's ISBN, 0070284695, finds the specific book: Child Psychology: A Contemporary Viewpoint.
Here are some other ISBNs you can use to try the Standard No. search: