1. ANSI X3.92-1981, “Data Encryption Algorithm,”, American National Standards Institute, New York (December 31, 1980).
2. Ayoub, F., “On the design of SP-networks,” presented at Eurocrypt’ 83, 21–23 March 83, Undine, Italy.
3. Bernhard, R., “Breaching system security,” Spectrum, vol. 19, pp. 24–31 (1982).
4. Davies, D. W., “Some regular properties of the Data Encryption Standard algorithm,” NPL note, presented at Crypto’ 81 (1981).
5. Davio, M., Desmedt, Y., Fosséprez, M., Govaerts, R., Hulsbosch, J., Neutjens, P., Piret, P., Quisquater, J. J., Vandewalle, J. & Wouters, P., “Analytical characteristics of the DES,” pp. 171–202, in Advances in cryptology: Proc. of CRYPTO’ 83, Santa Barbara, ed. D. Chaum, Plenum Publishing Corp., New York (1984).