Hello, Ian! Funny you should say, I've got a thread going for identifying tracks for Golden Book Video as I used to watch them as a child myself:
librarymusicthemes.com/index.php?topic=6063.0
They not only used APM Music, but De Wolfe, Capitol Media Music - The Professional, Southern Library of Recorded Music, Omnimusic (now part of APM Music), and the now dissolved distributor Emil Ascher, Inc. And there are only 63 unknown tracks left for all the titles combined!