I have no idea of the matter but I trust the reference book is correct. This is on the matter of who co-wrote the play Where the Rainbow Ends. The reference book cites that Reginald Owens was a co-writer which isn’t stated on Wikipedia. The reference book says he was the brain child of the play as well.
I have a good feeling the reference book is right, although I could be wrong. Clifford Mills is cited as the co-author (along with Reginald Owens) in the reference book. On Wikipedia, Clifford Mills wrote it with John Ramsey.
But where is Reginald Owen on that Wikipedia page? “It is perhaps not widely known that the famous children’s play Where the Rainbow Ends was the brain-child of Reginald Owen…” the reference book says (Page 13, Film Review 1973-74).