Reference
Ernesto Filippi, Massimo Capula, Luca M. Luiselli, Umberto Agrimi (1996): The spectrum of Natrix natrix (Linnaeus, 1758) and Natrix tessellata (Laurenti, 1768) in sympatric populations (Squamata: Serpentes: Colubridae). – Herpetozoa – 8_3_4: 155 - 164.