TY  - RPRT
TI  - Ecoregions of the conterminous United States: Evolution of a hierarchical spatial framework
AU  - James M. Omernik
AU  - Glenn E. Griffith
PY  - 2014
DO  - 10.1007/s00267-014-0364-1
UR  - https://pubs.usgs.gov/publication/70125309
ID  - 70125309
ER  -