1. C. L. Mantel, ?Batteries and energy systems?, McGraw-Hill, New York (1970) pp. 59?63.
2. V. S. Bagotzky and V. N. Flerov, ?Noveishie dostizhenia v oblasti khimicheskich istochnikov toka? Gos. Energ., Moscow, Leningrad (1963) p. 34.
3. M. Bonnemay, G. Bronoel, D. Doniat and E. Levart,Adv. Energ. Conv. 7 (1967) 159.
4. Bulgarian Patent Appl. no. 38 581.
5. I. Iliev, S. Gamburzev, A. Kaisheva, E. Vakanova, J. Muchovski and E. Budevski,Izv. Otd. Khim. Nauki, Bulg. Acad. Nauk 7 (1974) 223, 233.