Look for the bar code on the material, usually located on the back cover. There should be an ISBN code, either 10- or 13-digits long, depending on how recently the material was published, printed above the bar code. When no cover or bar code exists, you can use other methods to locate the number.
Locate the publication's copyright information. For books, this usually is contained on a page preceding the dedication or start of the book. For magazines, copyright information typically is in small print at the bottom of one of the early pages, like the table of contents. Locate the 10- or 13-digit number printed on the page.
Search an online book seller, such as Amazon or Barnes & Noble, for the book in question. The publication number can be located among the other product details, such as book length. When possible, the ISBN is displayed as both a 10- and 13-digit code.