TY  - RPRT
TI  - Observations of environmental change in Grand Canyon, Arizona
AU  - Robert H. Webb
AU  - Theodore S. Melis
AU  - Richard A. Valdez
PY  - 2002
DO  - 10.3133/wri024080
UR  - https://pubs.usgs.gov/publication/wri024080
ID  - wri024080
ER  -