| Reference | U. S. GEOLOGICAL SURVEY, U. S. BUREAU OF RECLAMATION, AND SOUTH DAKOTA GEOLOGICAL SURVEY, 1975 , MINERAL AND WATER RESOURCES OF SOUTH DAKOTA, SOUTH DAKOTA GEOLOGICAL SURVEY BULLETIN 16 { MULLEN, D. H., AND AGNEW, A. F., 1959 , THE MINERAL INDUSTRY OF SOUTH DAKOTA IN 1957 , SOUTH DAKOTA GEOLOGICAL SURVEY MINERALS REPORT 4 |