Stratigraphy of the Devonian Trimmers Rock in eastern Pennsylvania /

by Frakes, Lawrence A.
Harrisburg, Pa. : Commonwealth of Pennsylvania [Department of Internal Affairs, Bureau of Topographic and Geological Survey], 1967

Middle Devonian stratigraphy in central Pennsylvania : a revision /

by Faill, Rodger T., Hoskins, Donald M., Wells, Richard B.
Harrisburg, Pa. : Commonwealth of Pennsylvania [Department of Environmental Resources, Bureau of Topographic and Geological Survey], 1978