At this point I am thinking just getting a look at the various editions would be a majorly librarian type project. There must have been a couple dozen books in the original series. The old ones I had when I was a kid were gleaned from second-hand stores, which I left to a favorite teacher to be probably used to pieces; while slick-cover new editions were then already coming out that I disdained and never bought, not understanding that there might be some text alterations -- which I now run into as the "old" second-hand editions...