1. de Margerie E. Geologie. Polybiblion Revue Bibliographique Universelle. Partie litteraire. 1886;2(24):310-330
2. Bauer BO. Geomorphology. In: Goudie AS, editor. Encyclopedia of Geomorphology. London & New York: Taylor & Francis e-Library; 2006. pp. 428-435
3. Huggett RJ. Fundamentals of Geomorphology. Routledge Fundamentals of Physical Geography. New York: Taylor & Francis e-Library; 2005. p. 386
4. Klimaszewski M. Geomorfologia. 6th ed. Warszawa: PWN; 1980. p. 1063
5. Davis WM. The rivers and valleys of Pennsylvania. National Geographical Magazine. 1889;1:183-253. (Also in Geographical Essays)