References
Arntzen, J. W. (1978). Some hypotheses on postglacial migrations of the firebellied toad, Bombina bombina (Linnaeus) and the yellow-bellied toad, Bombina variegata (Linnaeus). Journal of Biogeography , 5, 339-345. https://doi.org/10.2307/3038027
Arntzen, J. W. (2018). Morphological and molecular characters to describe a marbled newt hybrid zone in the Iberian Peninsula.Contributions to Zoology, 87, 167-185.