1. Potentiometric-surface map of the Wyodak-Anderson Coal Bed, Powder River Structural Basin, Wyoming, 1973-84 Yale Public content 1986. 2002-06-01T04:00:00Z. 2009-02-23T19:50:48Z. Geological Survey (U.S.). The Survey ; Open-File Services Section, Western Distribution Branch. English. Public. Powder River Watershed (Wyo. and Mont.).