URBAN, Peter et al. Aquatic macrophyte vegetation and its relationship to the occurrence of the Eurasian otter (Lutra lutra) in the Hron River (Slovakia). In IUCN/SSC Otter Specialist Group Bulletin. - Luxembourg : IUCN/SSC Otter Specialist Group, 2010. ISSN 1023-9030, 2010, vol. 27, no. 3, pp. 158-165. Available on Internet: <http://www.otterspecialistgroup.org/Bulletin/Volume27/Vol27_Iss3_Index.html>