United States Geological Survey (USGS). (n.d.). National Land Cover Dataset 1992 - Pennsylvania; Unprojected/Geographic. State of Pennsylvania. http://www.pasda.psu.edu/uci/DataSummary.aspx?dataset=340

Available from: https://geo.btaa.org/catalog/d4a5ec81-fed9-4878-93d5-9334df3ce631