USGS Surficial Geologic Map Compilations (OFR 2006-1260). at <http://pubs.usgs.gov/of/2006/1260>

CalTopo - Backcountry topographic maps. at <http://caltopo.com/>

Recent USGS Publications for Massachusetts. at <http://pubs.er.usgs.gov/#search:advance/page=1/page_size=100/title=Massachusetts:0>

USGS Topoview. (2014). at <http://ngmdb.usgs.gov/maps/TopoView/>