By Barnett, H. L..
Minneapolis, Minnesota : Burgess, 1972

St. Paul, Minnesota : APS Press, 1996 0-89054-223-b

St. Paul, Minnesota : APS Press, 1998 0-89054-215-5

Minnesota : Lundquist, J.E., 2005 , COMPRA-F.C.A.C.C.Importaciones. 0-89054-334-8

Minnesota : Geological and Natural History Survey, 1887 .
n. : 22 cm.

By Thiel, George A..
Minneapolis : The University of Minnesota Press, 1944 .
506 p. : 24 cm.

By Grout, Frank F..
Minneapolis : The University of Minnesota, 1914 .
172 p. : 23 cm.