Letter to Arnold Carl Klebs, November 23, 1904
Letter to Arnold Carl Klebs, July 25, 1910
Letter to Arnold Carl Klebs, April 28, 1915
Letter to Arnold Carl Klebs, December 9, 1912
Letter to Arnold Carl Klebs, January 15, 1912
Letter to Arnold Carl Klebs, September 2, 1919
Letter to Arnold Carl Klebs, December 31, 1909
Letter to Arnold Carl Klebs, January 15, 1904
Letter to Arnold Carl Klebs, November 25, 1914
Letter to Arnold Carl Klebs, September 12, 1919