“…Progress of this work has been recorded in a number of papers by Hendricks (1936,1938,1939,1941,1942), Hendricks and Alexander (1939, 1940a, 1940b, Hendricks and Fry (1930), Hendricks andJefferson (1938, 1939), Hendricks, Nelson, and Alexander (1940), Hendricks and Ross (1938), and Ross (1943).…”