81-84. December 10, 1955. 4. Subspeciation in the meadow mouse, microtus pennsylvanicus, in Wyoming.
"A Review of the Middle American Tree Frogs of the Genus Ptychohyla"
William E. Duellman
W Reva, microtus ochrogaster and the meadow vole, M. pennsylvanicus, were trapped together.
"Mammals of Northwestern South Dakota"
Kenneth W. Andersen
It is known, however, to occur also in North Italy and in Bohemia, while microtus leucurus of the Pyrenees is identical with this species.
"The History of the European Fauna"
R. F. Scharff