Censorship in prison is a huge problem. Prisons or state departments of corrections often impose restrictive policies about who can send books to people in prison, and what kinds of books they can send. As a general rule, individuals cannot send books to people in prison. This is one major reason programs like the Prison Book Program have been created. In addition, many prison systems only allow books in if they are sent directly from a bookstore or a publisher. Others do not allow hardcover books, magazines or newspapers. Many require that the books be new, or that they arrive with an invoice, or that the prisoner request approval for the books in advance. And, certainly, some prisons deny entrance to certain books based on their content. As a result, the Prison Book Program cannot take it for granted that the books we send always reach their intended readers. Therefore, we send a postcard separate from each package of books, indicating which books we have sent and requesting that the prisoner contact us if the books do not arrive within a month. By tracking patterns of rejected books, we are able to confront prison systems about their restrictive policies and take administrative or legal action when necessary.