A fine collection of singable songs. Copies are still findable, and reasonable.

Amsco was a contemporary competitor, little books, also 35 cents, published by Amsco in the United States and Canadian Music Sales in Canada.
"Sing 'Em, Cowboy Sing 'Em!" contains 60 'songs of the trail and range.' I made a list some time ago, but I can't remember if I posted it. Editor W. J. Glassmacher, Arranger Charles E. Wilkenson.
If I haven't, I will start a thread for these Amsco song books.

This little book also is responsible for setting some kids on that downward path. It has guitar, 'ukulele and harmonica chords and notation, which I presume also were in the Robbins book.