Galerie Flechtheim (ed.), 'Einige Museumskäufe 1928-1929', in Junge Künstler, Berlin, 1929; Franz Roh, 'Detroit', in Der Cicerone, Leipzig, vol. 21, 1929, p. 479, illustrated ; Margaret Heiden, 'Neue deutsche Kunst im Detroit Inst. of Arts', in Museum der Gegenwart, 1932, vol. I, p. 16f, illustrated ; Parker Lesley, 'A Landscape by Carl Hofer', in Bulletin of the Detroit Institute of Arts, no. 6, March 1939, p. 6 (titled Portrait Head); 'Two painters show works', in Detroit Free Press, 19th March 1939; 'Hofer Landscape Gift to Museum', in The Detroit News, 19th March 1939; 'Hofer's Popularity, Begun at Carnegie, Grows', in The Art Digest, vol. 13, 1st May 1939, p. 15; Edgar P. Richardson, 20th Century Painting, Detroit, 1936, p. 42 (titled Girl's Head); Margaret Sterne, The Passionate Eye: The Life of William R. Valentiner , Detroit, 1980, p. 147; Gerhard Leistner, 'Nachgewiesene Museumsverkäufe durch die Galerie Flechtheim', in Alfred Flechtheim, Dusseldorf, 1987, p. 133 (titled Mädchenkopf); Karl Bernhard Wohlert & Markus Eisenbeis, Karl Hofer. Werkverzeichnis de Gemälde, Cologne, 2008, vol. II, p. 173, no. 861, illustrated