Biologisches Zentralblatt (G. Thieme, 1920)

Biologisches Zentralblatt (G. Thieme, 1921)

Biologisches Zentralblatt (G. Thieme, 1922)

Biology - Calkins, Gary N. (Gary Nathan), 1869 -1943 (Holt, 1914)

Biology - Nuffield Foundation. Science Teaching Project. (Longmans, 1968)

Biology - Calkins, Gary N. (Gary Nathan), 1869 -1943 (H. Holt and company, 1917)

Biology - Calkins, Gary N. (Gary Nathan), 1869 -1943 (H. Holt and company, 1914)