Dear smart people:
What procedure I should follow when someone denies that I do not own a copyright that in fact I do own?
I have been assigned the copyrights to my grandfather's books, and I'm even being paid royalties from the publisher of one of them. No one who is qualified to have an opinion has any doubt that I am the copyright holder. One particular user, on the other hands, knows that everyone else is wrong (and that I am lying).
The dispute is focused on an image of the cover of one of the books.
How can this be most effectively resolved?