Carola Giedion-Welcker. Paul Klee. New York, 1952, p. 12, 144, fig. 3b (unknown edition), locates it in the collection of Prof. L. Michaux [sic], Lausanne.
Eberhard W. Kornfeld. Verzeichnis des graphischen Werkes von Paul Klee. Bern, 1963, unpaginated, no. 2, ill., states that it was executed after Klee's return to Munich on August 5, 1901 and before his trip to Italy on October 22, 1901; lists three editions of this print, in the collections of Felix Klee, Bern; Mrs. L. Michaud, Lausanne; and a private collection, Bern.
Felix Klee in The Graphic Legacy of Paul Klee: An Exhibition of Klee's Prints. Exh. cat., Bard College. Annandale-on-Hudson, 1983, p. 14.
Jürgen Glaesemer in The Graphic Legacy of Paul Klee: An Exhibition of Klee's Prints. Exh. cat., Bard College. Annandale-on-Hudson, 1983, pp. 70, 80 n. 8, ill. p. 2 (not this edition), notes that it was made for Klee's old school friend, Louis Michaud, who was a medical student in 1901; translates the inscription by Goethe: "The spirit of medicine is easy to capture—FAUST".
Marcel Franciscono. Paul Klee. His Work and Thought. Chicago, 1991, pp. 32, 97, 146–47, fig. 8 (not this edition).
Josef Helfenstein and Christian Rümelin, ed. Paul Klee: Catalogue Raisonné. Ed. Paul Klee Foundation, Museum of Fine Arts, Berne. Vol. 1, 1883–1912. New York, 1998, p. 173, no. 143, ill.