STAFF BUREAU OF MINES BUMINES I.C. 8335 1967STAFF IND GEOL SUR CIR 266: COAL RESOURCES OF INDIANA P 15USGS B 708 HIGH GRADE CLAYS OF THE EASTERN USIND GEOL SUR REPORT OF PROGRESS NO 11 PENN UNDERCLAYSPETERS FRANK A. AND PAUL W. JOHNSON BUMINES I.C. 8648 1974PETERS FRANK A. ET.AL. BUMINES R.I. 6927 1967USBM TECHNICAL PAPER 417: ANALYSES OF INDIANA COALS 1927