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2. G. W. Morey, ?The Properties of Glass?, 2nd edn. (Reinhold, New York, 1954).
3. P. M. Sutton, ?The Dielectric Properties of Glass?, edited by J. B. Birks (Heywood, London, 1960) p. 113.
4. J. M. Stevels, Handbuch der physik20 (1957) 350.
5. N. M. Tallan, ?Electrical conductivity in ceramics and glass?, Part B (Marcel Dekker, New York, 1974).