1. German Patent (Offenlegung, 1496176, 1969).
2. French Patent 1436504 (1966).
3. French Patent 1486723 (1967).
4. Böhm, H., and Pohl, F. A., Wiss. Ber. AEG-Telefunken, 41, 46 (1968).
5. Böhm, H., and Pohl, F. A., 3, Journées Internat. d'Etude des Piles à Combustible (Brussels, June 1969).