Invia SMS: Geology of the conterminous United States at 1:2,500,000 scale : a digital representation of the 1974 P.B. King and H.M. Beikman map / U.S. Department of the Interior, U.S. Geological Survey ; by Paul G. Schruben, Raymond E. Arndt, and Walter J. Bawiec ; display software by Russell A. Ambroziak.