TY  - RPRT
TI  - Symbols for 1:50,000-scale 15-minute quadrangle topographic maps of the United States
AU  - Members of the Engineering Geology and Ground Water Branches, U.S. Geological Survey
PY  - 1977
DO  - 10.3133/70101777
UR  - https://pubs.usgs.gov/publication/70101777
ID  - 70101777
ER  -