TY  - RPRT
TI  - Lower middle ordovician of south-central Pennsylvania
AU  - Lawrence C. Craig
PY  - 1949
DO  - 10.1130/0016-7606(1949)60[707:lmoosp]2.0.co;2
UR  - https://pubs.usgs.gov/publication/70215520
ID  - 70215520
ER  -