Book publishing contracts are official legal agreements made between authors and publishers. Contract terms may include who is granted the copyright to the published work. Generally, authors wish to retain the copyright to their creative work, however in some cases a "grant of rights" clause may be included in a publishers contract, which transfers copyright ownership to the publisher. In the case of a "work for hire" publication, where an author is hired to write a specific publication for a publisher, such as a textbook, then the publisher usually owns the exclusive copyrights to the work under the terms of the publishers contract. Other items such as advance payments and royalties from future sales may be addressed in a publishers contract. Both the author and the publisher's rights regarding film adaptations of the literary work may also be included. It is recommended that an author have a publishers contract reviewed by an experienced attorney before signing a contract to ensure that the contract is fair and legally valid.