2 literature references for Vulpes lagopus (Linnaeus, 1758):

Author: Rice, Dale W.
Year: 1998
Title: Marine Mammals of the World: Systematics and Distribution
Source: Special Publications of the Society for Marine Mammals, no. 4
Author: Wilson, Don E., and DeeAnn M. Reeder, eds.
Year: 2005
Source: Mammal Species of the World: A Taxonomic and Geographic Reference, 3rd ed., vols. 1 & 2