TY  - RPRT
TI  - Maps showing natural aggregates of the conterminous United States
AU  - William H. Langer
AU  - Donna A. Belval
PY  - 1983
DO  - 10.3133/ofr83743
UR  - https://pubs.usgs.gov/publication/ofr83743
ID  - ofr83743
ER  -