Digital Versions of Older NEIGC Guidebooks (1920-1989). at <http://www.library.unh.edu/digital/category/science-technology>

Scanned "newer" 1:25K topographic maps (from MassGIS). at <http://www.mass.gov/anf/research-and-tech/it-serv-and-support/application-serv/office-of-geographic- information-massgis/datalayers/imquad.html>

UNH Historic Map Library for New England. at <http://docs.unh.edu/nhtopos/nhtopos.htm>

USGS Groundwater Watch. at <http://groundwaterwatch.usgs.gov/>

USGS Water Resources of Massachusetts and Rhode Island. at <http://ma.water.usgs.gov/>