1. Complete Bouguer gravity anomaly map of the International Falls 1⁰?x 2⁰?quadrangle, Minnesota and Ontario [microform] Yale Public content 1988. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). U.S. Geological Survey : [Books and Open-File Reports Section, distributor. English. Public. Minnesota and Ontario.