L. R. Ladwig

Map, directory, and statistics of permitted Colorado coal mines, 1983. [Colorado]

P. Rushworth, B. S. Kelso, L. R. Ladwig, 1984 .

RS-05 Coal Resources of the Denver and Cheyenne Basins, Colorado

L. R. Ladwig, R. M. Kirkham, R. Kirkham, 1979 .

OF-77-01 Preliminary Investigation and Feasibility Study of Environmental Impact of Energy Resource Development in the Denver Basin

L. R. Ladwig, R. M. Kirkham, R. Kirkham, 1977 .

SP-36 1990 Summary of Coal Resources in Colorado

L. R. Ladwig, R. Holt, D. K. Murray, 1990 .