Google Book Search seems to indicate that the words and music to I MAY NOT PASS THIS WAY AGAIN are included in a school songbook called "Exploring Music" by Eunice Boardman and Beth Landis, New York: Holt, Rinehart and Winston, 1971, page 9.

However, only "snippets" are viewable at Google Book Search; hence my uncertainty. But if I am reading the tiny print correctly, the songwriter is Rod McKuen. Can anyone confirm this?