Book copyright law allows for what is called "fair use" when quoting or using parts of a book in a separate work. Fair use allows a third party to quote from a copyrighted work with proper attribution. Other laws allow the use of copyrighted material from a book for parody. Book copyright law does not allow anyone who is not the legal copyright holder to copy or make derivative works of a copyrighted book. For example, writing a theatrical adaptation of a copyrighted book without permission from the copyright holder is in violation of copyright law. In some cases, the author of a book is the copyright holder, however this is not always the case. In some cases, the publisher of a book may own the copyright to the book, especially in the case of a "work for hire" book, such as a textbook. Inexperienced authors also sometimes sign away the copyright to their creative works when they sign publishing contracts.