TY  - RPRT
TI  - Factors related to the water-yielding potential of rocks in the Piedmont and Valley and Ridge provinces of Pennsylvania
AU  - D.S. Knopman
PY  - 1990
DO  - 10.3133/wri904174
UR  - https://pubs.usgs.gov/publication/wri904174
ID  - wri904174
ER  -