Não informado. (2001). Bulletin of the Pennsylvania Geological Survey. Pennsylvania Geological Survey.
Style de citation Chicago (17e éd.)Não informado. Bulletin of the Pennsylvania Geological Survey. Harrisburg, Pa: Pennsylvania Geological Survey, 2001.
Style de citation MLA (8e éd.)Não informado. Bulletin of the Pennsylvania Geological Survey. Pennsylvania Geological Survey, 2001.
Attention : ces citations peuvent ne pas être correctes à 100%.