LC in OCLC, 3/24/94 (hdg.: Krüger, Gustav, 1862-1940)
OCLC, April 22, 1999 (hdgs.: Krüger, Gustav, 1862-1940; Krüger, Gustav, b. 1862; Krueger, Gustav, 1862-1940; usage: Gustav Krüger; G. Krüger; Gustav Kruger)
The immortality of man, 1927 t.p. (Gustav Krüger)