Smith, Jr., L.B., Read, J.F., 2000. Rapid Onset of Late Paleozoic Glaciation on Gondwana: Evidence from Upper Mississippian Strata of the Midcontinent, United States. Geology 28, 279-282. doi:10.1130/0091-7613(2000)28<279:ROOLPG>2.0.CO;2