ZADIK (the Zentralarchiv des internationalen Kunsthandels) has digitised the records of the following dealers covering the noted dates.
These are all now searchable online;
Galerie Der Spiegel of Köln 1945-1993;
Galerie Zwirner Essen and Köln, from1953;
Moderne Galerie Otto Stangl of München 1949-1991;
Galerie Inge Baecker of Bpchum and Köln, from 1970;
Galerie Parnass of Wuppertal-Elberfeld 1949-1965;
Edition & Galerie Hundertmark of Berlin, Köln, Frankfurt and Gran Canaria, from 1970;
Galerie Michael Hertz of Bremen 1931-1981;
Galerie Erhard Klein of Bonn and Bad Münstereifel-Mutscheid, from 1970;Galerie Rudolf Springer of Berlin from 1948; Galerie Heiner Friedrich of München and Köln from 1963;
Galerie Aachen of Aachen 1965-1967;
Galerie Heinz Teufel of Koblenz, Köln, Mahlberg and Dresden 1966-1996;
Galerien Thannhauser of München, Luzern, Berlin, Paris, (New York) 1919-1971;
Galerie Dorothea Loehr of Frankfurt 1959-1993;
Kritikerin Anna Klapheck of Düsseldorf 1929-1986;
Kritiker Albert Schulze of Vellinghausen 1905-1967;
and Mary Bauermeister from 1951 (in process).
For further information, access the online records here. Click here to visit the Zadik homepage.