H. E.  Quick, ?British slugs (Pulmonata: Testacellidae, Arionidae, Limacidae)?, Bulletin of the British Museum (Natural History), Zoology, vol. 6, pp. 103-226, 1960.

M. P.  Kerney and Cameron, R. A. D., Land Snails of Britain and North-West Europe. Hong Kong: Harper Collins Publishers, 1979.

A.  Wiktor, ?The slugs of Bulgaria (Arionidae, Milacidae, Limacidae, Agriolimacidae - Gastropoda, Stylommatophora)?, Annales Zoologici, vol. 37, pp. 71-205, 1983.