2020. U.S. Geological Survey, Southwest Region. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States (https://doi.org/10.5066/F7WH2N65) represents a seamless, s... Montgomery County, Pennsylvania.
2018. Digitized regional surficial geology map for northwestern Pennsylvania. The complete citation for the paper map is: Map of the Glacial Deposits of ... Allegheny College.