1. Las Animas Formation (upper Precambrian) in the subsurface of southeastern Colorado Author/Creator: Tweto, Ogden, 1912-1983 Publication/Creation: [Washington, D.C.] : U.S. Dept. of the Interior, U.S. Geological Survey, 1983 Resource Type: Book Access & Availability: Loading
2. Late Precambrian Sixtymile Formation and orogeny at top of the Grand Canyon Supergroup, northern Arizona Author/Creator: Elston, Donald Parker, 1926- author Publication/Creation: Washington : United States Department of the Interior, Geological Survey, 1979 Resource Type: Book Access & Availability: Loading