Coal Resource Classification System of the U.S. Geological Survey
By Gordon H. Wood, Jr., Thomas M. Kehn, M. Devereux Carter, and William C. Culbertson
GEOLOGICAL SURVEY CIRCULAR 891
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| Figure 14 - A ridge with constructions of 14-inch minimum thickness limit |
Created by the EERT WWW Staff.
U.S. Department of the Interior, U.S. Geological Survey
URL: http://pubs.usgs.gov/circ/c891/figures/figure14.htm
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