Preliminary geologic map of the Howardsville 7.5-minute quadrangle, San Juan and Hinsdale counties, Colorado /

[Reston, Va.?] : U.S. Geological Survey, 1996

Preliminary geologic map of the eastern and northern parts of the Topock 7.5-minute quadrangle, Arizona and California /

by Howard, Keith A., John, Barbara E., Nielson, Jane E.
[Reston, Va.?] : U.S. Geological Survey, 1997