TY  - RPRT
TI  - National geophysical data grids; gamma-ray, gravity, magnetic, and topographic data for the conterminous United States
AU  - Jeffrey D. Phillips
AU  - Joseph S. Duval
AU  - Russell A. Ambroziak
PY  - 1993
DO  - 10.3133/ds9
UR  - https://pubs.usgs.gov/publication/ds9
ID  - ds9
ER  -