1st National Symposium 1976, Mississippi State University, USA 2nd Symposium 1979, Ann Arbor Michigan, USA 3rd International Symposium 1982, San Diego, California, USA 4th Symposium 1987, Indianapolis, Indiana, USA 5th International Symposium 1993, Montreal, Québec, Canada 6th International Symposium 1997, New Orleans, Louisiana, USA 7th International Symposium 2000, Calgary, Alberta, Canada   8th International Symposium September 12-16, 2004, in Saratoga Springs, New York, USA