According to Hank Davis and Colin Escott in their notes to the Sun Blues Years box set, when it first appeared, 'Mystery Train was credited solely to Junior Parker and published by Memphis Music. By the time Elvis Presley recorded his version in 1955, Sam Phillips had added his name to the copyright and the publishing had been tranferred to Phillips' Hi Lo Music. They suggest this was possibly in part settlement of Junior Parker's contract dispute.

--Stewie.