E. Heske

Sexual dimorphism and mating systems in voles
Ostfeld, Richard S., and E. J. Heske. 1993. “Sexual Dimorphism and Mating Systems in Voles”. J. Mammal 74: 230-33. http://www.caryinstitute.org/reprints/Ostfeld_and_Heske_1993_J_Mammal_74_230-233.pdf.
Sexual dimorphism in size, relative size of testes, and mating systems of North American voles
Heske, E. J., and Richard S. Ostfeld. 1990. “Sexual Dimorphism in Size, Relative Size of Testes, and Mating Systems of North American Voles”. J. Mammal 71: 510-19.