(EN) Kevin Cummings, Arnold Edward Ortmann, su cummings.inhs.illinois.edu, University of Illinois at Urbana–Champaign. URL consultato il 4 settembre 2024.
(EN) Charles H. Smith, Ortmann, Arnold Edward (Prussia-United States 1863-1927), in Some Biogeographers, Evolutionists and Ecologists: Chrono-Biographical Sketches, Western Kentucky University, 2005. URL consultato il 5 agosto 2013.