There is a big factual inaccuracy; A Boy Named Sue was written by Shel Silverstein, nor Shelby Singleton! Singleton is the guy who bought the Sub Records catalog from Dam Phillips. Cash would have never made such a mistake, or would he ?
Nope, He wouldn't have. He gave credit for the song to Shel on stage at Madison Square Garden in the 1970's However, this letter wasn't written by John R. Cash :(