1. Engineering Physics Laboratory, E.I. du Pont de Nemours & Company (Inc.), Wilmington, DE 19898.
2. Central Rescarch and Development Department, E.I. du Pont de Nemours & Company (Inc.), Wilmington, DE 19898.
3. Medical Products Department, E.I. du Pont de Nemours & Company (Inc.), Wilmington, DE 19898.