1. Water Resources Division, U.S. Geological Survey; MS 413, Box 25046, Denver Federal Center Lakewood CO 80215-0046
2. Dep. of Mathematics; Univ. of Colorado; P.O. Box 173364, Campus Box 170 Denver CO 80217-3364
3. USDA-ARS-NPA, Natural Resources Research Center, Soil-Plant-Nutrient Research Unit; P.O. Box E Ft. Collins CO 80522-0470
4. NASA Ames Research Center, Earth Science Division, Johnson Controls World Services; SGE:239-20 Moffett Field CA 94035-1000