Grout, Frank F. (Frank Fitch), 1880-1958, Schwartz, George M. (George Melvin), 1892-1980, Sharp, R.P. (Surveyor) (1959). Geology of Cook County, Minnesota, Bulletin 39, Plate 14. Minnesota Geological Survey. https://reflections.mndigital.org/catalog/mgs:1050 (map)