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3. M.A. Lampert, P. Mark: Current Injection in Solids ( Academic Press, New York 1970 )
4. D.L. White: J. Appl. Phys. 33, 2547 (1962)
5. N.I. Meyer, M.H. Jørgensen: Festkörperprobleme X, ed. by 0. Madelung ( Pergamon, Vieweg 1970 ) p. 21