TY - BOOK ID - 137687060 TI - Observations of environmental change in Grand Canyon, Arizona AU - Webb, Robert H. AU - Melis, Theodore S. AU - Valdez, Richard A. AU - Grand Canyon Monitoring and Research Center. AU - Geological Survey (U.S.) PY - 2002 PB - Tucson, Ariz. : U.S. Geological Survey ; Denver, CO : U.S. Geological Survey, Information Services [distributor], DB - UniCat KW - Grand Canyon (Ariz.) KW - Environmental conditions KW - History. UR - https://www.unicat.be/uniCat?func=search&query=sysid:137687060 AB - ER -