I can only answer your question to a certain extent, as particular facts of your case could cause my answer to change. You would be best advised to seek the opinion of an attorney before deciding how to proceed. A written agreement is only necessary, where the employee wishes to keep his rights under the copyright laws. Application of this statute to your situation depends upon your relationship to the publisher and author of the work and matters of control over the work. 17 USC 106A , Moral Rights of Authors, should be your next stop.
Authors do have the right to keep their names attached to their works.