1    Das Haus der Frau: privately published Artist Lexicon (book + PDF 

2    Dresslers Kunsthandbuch 1930: professional PDF version.

3    Martin Erich Philipp: Catalogue Raisonné (Werkverzeichnis) (PDF) 

      including Else Staps (wife) and Walter Helfenbein (student).

(Click pictures for details)