TY  - RPRT
TI  - Geologic characterization of natural aggregate; a field geologist's guide to natural aggregate resource assessment
AU  - William H. Langer
AU  - Daniel H. Knepper
PY  - 1995
DO  - 10.3133/ofr95582
UR  - https://pubs.usgs.gov/publication/ofr95582
ID  - ofr95582
ER  -