TY  - RPRT
TI  - Map showing areas that correlate with subsidence events due to underground mining in Armstrong, Beaver, and Butler Counties, Pennsylvania
AU  - K.O. Bushnell
AU  - R. P. Briggs
PY  - 1976
DO  - 10.3133/mf693d
UR  - https://pubs.usgs.gov/publication/mf693D
ID  - mf693D
ER  -