Simple Bouguer gravity map of Massachusetts [cartographic material] / Department of the Interior, United States Geological Survey ; by Randolph W. Bromery ; prepared in cooperation with the Commonwealth of Massachusetts, Department of Public Works
"Map compiled from approximately 3700 gravity stations established by R.W. Bromery 1961-63, W.H. Diment 1953, and W.R. Joyner 1958. Gravity data compiled by H.S. Sherman."