Copyright can be tricky, and to be honest it’s a bit of a maze figuring out what to do. The Samuelson Clinic on Berkley has some help for you.
The Clinic has just published a handbook to determining whether copyrighted material is inside or outside the public domain.
These educational tools help users to evaluate the copyright status of a work created in the United States between January 1, 1923 and December 31, 1977—those works that were created before today’s 1976 Copyright Act.
The tool still requires some participation from the user but is a good guideline.