Series I. Correspondence, features incoming correspondence from artists and writers, art critics and collectors, publishers, cultural institutions and organizations, such as museums, galleries, and foundations, and others. Large files exist for the Bollingen Foundation, advertising agent Marcus Brumwell, publisher Lund Humphries Ltd, art critics Marcel Joray and Sir Herbert Read, Lewis Mumford, artist and curator Willem Sandberg, curator James Johnson Sweeney, and the Tate Gallery in London, among others. There are smaller files for numerous well-known early Twentieth century artists, including Anni and Joseph Albers, Hans Arp, Henri Cartier-Bresson, Ivan and Serge Chermayeff, Katherine Dreier, Marcel Duchamps, Walter Gropius, Hans Richter, and Kurt Schwitters.