Supporting the Moe Jaffe and Dwight Latham authorship is a record at the American Society of Composers, Authors and Publishers.

You can look at their record here; you have to enter the name in the search field because I couldn't link directly to the page. Past the following into the search field:

I m my own grandpa

That should bring up the record. As far as reliablity of this info, I can't say. But it looks fairly professional.

Jack