2 literature references:

Author: Holcík, J. and C.B. Renaud
Year: 1986
Title: Eudontomyzon mariae (Berg, 1931).
Source: p. 165-185. In J. Holcík (ed.) The Freshwater fishes of Europe. Vol.1, Part I, Petromyzontiformes.
Author: FAO-FIES
Year: 2010
Title: Aquatic Sciences and Fisheries Information System (ASFIS) species list.
Source: Retrieved from http://www.fao.org/fishery/collection/asfis/en, March 2010.