The geology of Pennsylvania; a government survey, by Henry Darwin Rogers, State Geologist.

Chicago citation style
Pennsylvania. State Geologist (1836-1841). The geology of Pennsylvania; a government survey, by Henry Darwin Rogers, State Geologist.. Retrieved from the Digital Public Library of America, https://archive.org/details/geologyofpennsyl00penn_0. (Accessed September 22, 2018.)
APA citation style
Pennsylvania. State Geologist (1836-1841), The geology of Pennsylvania; a government survey, by Henry Darwin Rogers, State Geologist.. Retrieved from the Digital Public Library of America, https://archive.org/details/geologyofpennsyl00penn_0
MLA citation style
Pennsylvania. State Geologist (1836-1841). Retrieved from the Digital Public Library of America <https://archive.org/details/geologyofpennsyl00penn_0>.
Note: These citations are programmatically generated and may be incomplete.