STAFF BUREAU OF MINES BUMINES I. C. 8335 1967.PETERS FRANK A. ET. AL. BUMINES R. I. 6927 1967.STOUT WILBER ET. AL. OHIO DIV OF GEOL SUR 4TH SER BULL 26 19STOUT WILBER OHIO DIV OF GEOL SUR 4TH SER BULL 40 1940.HOOVER KARL ET. AL. OHIO DIV OF GEOL SUR I. C. 24 1959.