(en) Petronio, C. (1995): Note on the taxonomy of Pleistocene hippopotamuses. Ibex3: 53-55. PDF fulltext
uni-bonn.de
neandertal.uni-bonn.de
(en) "150 Years of Neanderthal Discoveries; Early Europeans - Continuity & Discontinuity," ed. von Koenigswald, Wighart and Thomas Litt, TERRA NOSTRA 2006/2 Université de Bonn, in PDF