Coal. Investigations of coal fields of Colorado, New Mexico, Utah, Oregon, and Virginia by Survey in 1907, with bibliography of Survey papers relating to coal, coke, lignite, and peat; [articles] by H. S. Gale, W. T. Lee, J. H. Gardner, G. B. Richardson, J. S. Diller, W. C. Mendenhall, C. A. Fisher, and J. M. Nickles.