CUMMINGS J B REPT OF S DAK STATE PLANNING BOARD 1936 TUNGSTEG IN SOUTH DAKOTA P 29GEOL SURVEY BULL 380 1909 P 154SOUTH DAKOTA SCHOOL OF MINES BULL 17 1937 P 166SOUTH DAKOTA SCHOOL OF MINES BULL 12 1918 P 62SOUTH DAKOTA SCHOOL OF MINES BULL 10 1914 P 220U S BUREAU OF MINES INFO CIRC 7707 P 49 50