Letter to Arnold Carl Klebs, February 18, 1904
Letter to Arnold Carl Klebs, January 12, 1906
Letter to Arnold Carl Klebs, January 15, 1904
Letter to Arnold Carl Klebs, January 21, 1904
Letter to Arnold Carl Klebs, January 8, 1906
Letter to Arnold Carl Klebs, March 8, 1904
Letter to Arnold Carl Klebs, November 23, 1904
Letter to Arnold Carl Klebs, November 23, 1904
Letter to Arthur Thomson, 1904
Letter to Arthur Thomson, January 13, 1905