1. D. Berndt, Maintenance-Free Batteries, 2nd edn., Research Studies Press, Taunton, Somerset, England, 1997.
2. D.H. McClelland, J.L. Devitt, US Patent 3,862,861 (1972).
3. B. Culpin, J.A. Hayman, in: L.J. Pearce (Ed.), Power Sources 11, International Power Sources Symposium Committee, Leatherhead, UK, 1986, p. 45.
4. Influence of separator structure on the performance of valve-regulated batteries
5. G.C. Zguris, D.W. Klauber, N.L. Lifshutz, in: T. Keily, B.W. Baxter (Eds.), Power Sources 13, International Power Sources Symposium Committee, Leatherhead, UK, 1991, p. 45.