Google is your friend.
The best bibliographies of a series are always by the ‘fans’ (or dealers) of the series.
Google is the best way to find them. There’s no single good reference for this.
Another option is to go to ABEBOOKS, where book descriptions are sometimes quite elaborate, and find a high-line book dealer, the kind who publishes a paper catalog, who is listing what you’re looking for. They often give enough information that you get an idea of exactly what should be in the set.
Amazon kinda’ works for that too, but more amateurs list on Amazon.