TY  - RPRT
TI  - Four reference soil and rock samples for measuring element availability in the Western Energy Regions
AU  - J.G. Crock
AU  - R. C. Severson
PY  - 1980
DO  - 10.3133/cir841
UR  - https://pubs.usgs.gov/publication/cir841
ID  - cir841
ER  -