TY  - RPRT
TI  - International strategic minerals inventory summary report; niobium (columbium) and tantalum
AU  - R.N. Crockett
AU  - D. M. Sutphin
PY  - 1993
DO  - 10.3133/cir930m
UR  - https://pubs.usgs.gov/publication/cir930M
ID  - cir930M
ER  -