1. USDA Agricultural Research Service North Central Soil Conservation Research Lab. Morris MN 56267 USA
2. Univ. of Wyoming Laramie WY 82071 USA
3. Science Dep. Bergen County Technical Schools – Teterboro Teteroboro NJ 07608 USA
4. Land O'Lakes WinField United Arden Hills MN 55112 USA
5. Dep. of Agronomy and Plant Genetics Univ. of Minnesota St. Paul MN 55108 USA
6. USDA Agricultural Research Service Soil and Water Management Research Unit St. Paul MN 55108 USA
7. Southwest Research & Outreach Center Univ. of Minnesota Lamberton MN 56152 USA