In the version that the Weavers sing, and also Trini Lopez which was the big seller of this version, all the verses were written by David Lazar, Larry Ehrlich and Tom Six, which is a non de plume for the Weavers. The only lyrics that Paul Clayton supplied are those of the chorus. As I said earlier the Grammer version has totally different lyrics. David Lazar also wrote a much better song, Rr. Freud. Incidentally in answer to someone above who asked to whom one paid roayalties BMI controls the royalties to both Gotta Travel On and Dr. Freud.