1. School of Forest Resources and Conservation and Food and Resource Economics Dep., P.O. Box 110410 IFAS; Univ. of Florida; Gainesville FL 32611-0410
2. Food and Resource Economics Dep., P.O. Box 110410 IFAS; Univ. of Florida; Gainesville FL 32611-0240
3. Texas A&M AgriLife Extension Service; Dep. of Soil and Crop Sciences, 370 Olsen Blvd., 2474 TAMUS; Texas A&M Univ.; College Station TX 77843
4. Biosystems and Agricultural Engineering Dep. 218 Agriculture Hall; Oklahoma State Univ.; Stillwater OK 74078-6021
5. Environmental Science Program, P.O. Box 442339; Univ. of Idaho; Moscow ID 83844-2339