TY  - RPRT
TI  - Ordovician graptolites from the northern Sierra de Cobachi, Sonora, Mexico
AU  - John F. Riva
AU  - Keith B. Ketner
PY  - 2011
DO  - 10.1017/s0263593300014401
UR  - https://pubs.usgs.gov/publication/70208973
ID  - 70208973
ER  -