National coal resource assessment non-proprietary data: Location, stratigraphy, and coal quality for selected tertiary coal in the Northern Rocky Mountains and Great Plains region - Flores, Romeo; Ochs, A.M.; Stricker, G.; Ellis, M.S.; Roberts, S.; Keighin, C.; Murphy, E.C.; Cavaroc Jr., V.V.; Johnson, R.; Wilde, E.M. (Open-File Report, 1999)