I noted your comment re. my art units. They are all original...original to ME and written BY me. 90% of the ideas are from MY head.
You MIGHT consider them "old books." As I used to distribute them and sell them in the 90's for $15. each. They were very popular as there was nothing like them in Canada. Distributed by a publisher out West by mail order.
I decided to make them available on TpT for $5 now that I am retired for the benefit of the next generation. They ARE old books...but they are MY books. And a real bargain at $5.