1. Kernforschungszentrum Karlsruhe Laboratorium fur Aerosolphysik und Filtertechnik I, Postfach 3640 7500 Karlsruhe 1, Federal Republic of Germany
2. Oak Ridge National Laboratory, P.O. Box X, Oak Ridge, Tennessee 37831
3. Electric Power Research Institute 3412 Hillview Avenue, Palo Alto, California 94301