Cothran, Gus (1984). "Morphologic Relationships of the Hybridizing Ground Squirrels Spermophilus mexicanus and S. Tridecemlineatus". Journal of Mammalogy. 64 (4): 591–602. doi:10.2307/1380514. JSTOR1380514.
Cothran, Gus (1984). "Morphologic Relationships of the Hybridizing Ground Squirrels Spermophilus mexicanus and S. Tridecemlineatus". Journal of Mammalogy. 64 (4): 591–602. doi:10.2307/1380514. JSTOR1380514.