TY  - RPRT
TI  - Niobium and tantalum
AU  - Klaus J. Schulz
AU  - Nadine M. Piatak
AU  - John F. Papp
PY  - 2017
DO  - 10.3133/pp1802m
UR  - https://pubs.usgs.gov/publication/pp1802M
ID  - pp1802M
ER  -