Nolo's Plain-English Law Dictionary

Copyright Notice

The formal notice consisting of the copyright symbol (or word, copyright), plus the date of publication and the owner's name, placed on published copies of a copyrighted work. For works published in the U.S. after March 1, 1989, copyright notice is not required. A notice is still useful to remind others that the work is copyrighted, to steer a would-be user in the right direction to obtain permission, and to preclude a defense of "I didn't know it was copyrighted" if someone uses the copyrighted material without permission. (See also: published work)