1. U.S. Environmental Protection Agency; Office of Research and Development; National Health and Ecological Effects Research Laboratory; Mid-Continent Ecology Division; Duluth MN U.S.A
2. University of Minnesota - Duluth; Duluth MN U.S.A
3. University of Vermont; Burlington VT U.S.A
4. U.S. Geological Survey; Lake Superior Biological Station; Ashland WI U.S.A