Não informado. (2001). Bulletin of the Pennsylvania Geological Survey. Pennsylvania Geological Survey.
Chicagoスタイル(17版)引用形式Não informado. Bulletin of the Pennsylvania Geological Survey. Harrisburg, Pa: Pennsylvania Geological Survey, 2001.
MLA(8版)引用形式Não informado. Bulletin of the Pennsylvania Geological Survey. Pennsylvania Geological Survey, 2001.
警告: この引用は必ずしも正確ではありません.