H. Bittner, Käthe Kollwitz Drawings, New York, 1959, p. 26, no. 69 (illustrated; dated 1918, titled Nachdenken).
O. Nagel, The Drawings of Käthe Kollwitz, New York, 1972, p. 334, no. 737 (illustrated, p. 335).
New Jersey, The Montclair Art Museum, The Moses and Ida Soyer Collection, September-October 1971, no. 57 (titled Contemplation).
The Jersey City Museum, Selections from the Moses and Ida Soyer Collection, February-May 1991.