His Beiträge, 1898-

LCCN 25-4567: His The mentality of apes, 1925 (hdg.: Köhler, Wolfgang, 1887-1967; usage: Wolfgang Köhler)

The mentality of apes, 1951: t.p. (Wolfgang Köhler; prof. of philos., Univ. of Berlin)

Wikipedia, Apr. 18, 2019 (Wolfgang Köhler; b. 21 January 1887 in Tallinn, Estonia; d. 11 June 1967 in Enfield, New Hampshire; German psychologist and phenomenologist who, like Max Wertheimer, and Kurt Koffka, contributed to the creation of Gestalt psychology) https://en.wikipedia.org/wiki/Wolfgang_K%C3%B6hler