Art writer, owner of the Downtown Gallery in New York; speaker at the 2nd American Artists' Congress 1937 in New York, N.Y., a symposium held Jan. 13, 1937 at the Museum of Modern Art, New York. The speakers included Walter Quirt, Salvador Dali, Meyer Schapiro, Klein, and Richard Huelsenbeck. Klein was also one of the participants at the famous, informal gathering of art scholars organized by Schapiro around 1935 that included Robert Goldwater, Alfred H. Barr, Jr., Erwin Panofsky, James Johnson Sweeney and occasionally Lewis Mumford.
Marquis, Alice Goldfarb. Alfred H. Barr, Jr.: Missionary for the Modern. Chicago: Contemporary Books, 1989, p. 125.