About the royalties: yeah, I once read about this in an interview of Earl Zero in the Natty Dread magazine.
The song is fully credited to Earl Zero (I still have the original "Egyptian Reggae" 7'' with Richman as the author). Earl Zero and Mr. Richman met once after a Richman gig and settled the thing amicably. It turned out that Jonathan Richman didn't know about the original author of the tune at all, and he was slightly alarmed at first about this dread in front of him.
According to Earl Zero - by the way - he had filed himself as the author already in the 70's in JA. Johnnie Clarke handed over the rights in all friendship, but the one hard nut to crack was Bunny Lee...
