Might I suggest that you get hold of a copy of a book by John van Riemsdijk ISBN 0-906899-61-3 Compound Locomotives An International Survey. It isn't perfect but it covers quite a bit of ground, I hope that the printed sources section might prove of use to you and you will find not only a list of English language publications but French, German, Dutch and Italian too. Let me know how you get on. Wet steam is only a part of the story, why should you think about the compound story purely within this narrow widow? Porta, Chapelon, De Casso and many others worked with superheated steam. Read the book and you will learn about Wilhelm Schmidt and his unthinking disciple Robert Garbe. There are reasons why the BR 01 is rated at close on 1,500 hp less than the 231E.