Kortum, Gerhard (1996). "The German Challenger of Neptune"(PDF). The History of Oceanography Newsletter. No. 8. International Union of the History and Philosophy of Science. pp. 3–6. ISSN1013-3917. Archived from the original(PDF) on 7 October 2010.
Kortum, Gerhard (1996). "The German Challenger of Neptune"(PDF). The History of Oceanography Newsletter. No. 8. International Union of the History and Philosophy of Science. pp. 3–6. ISSN1013-3917. Archived from the original(PDF) on 7 October 2010.
Kortum, Gerhard (1996). "The German Challenger of Neptune"(PDF). The History of Oceanography Newsletter. No. 8. International Union of the History and Philosophy of Science. pp. 3–6. ISSN1013-3917. Archived from the original(PDF) on 7 October 2010.