Não informado. (1922). 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, 1922.
MLA(8版)引用形式Não informado. Bulletin of the Pennsylvania Geological Survey. Pennsylvania Geological Survey, 1922.
警告: この引用は必ずしも正確ではありません.