Pocock, R. I (1935). „The Races of Canis lupus”. Proceedings of the Zoological Society of London. 105 (3): 647—686. doi:10.1111/j.1096-3642.1935.tb01687.x.
Chambers SM, Fain SR, Fazio B, Amaral M (2012). „An account of the taxonomy of North American wolves from morphological and genetic analyses”. North American Fauna. 77: 1—67. doi:10.3996/nafa.77.0001.