Borchert, J. R. (1987). America's northern heartland. University of Minnesota Press.
Dyfyniad Arddull ChicagoBorchert, John R. America's Northern Heartland. Minneapolis: University of Minnesota Press, 1987.
Dyfyniad MLABorchert, John R. America's Northern Heartland. University of Minnesota Press, 1987.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.