1. E.R.Berlekamp, R.J.Mc Eliece and H.C.A. Van Tilborg, On the inherent intractability of certain coding problems, IEEE Trans. Inform. Theory, (1978) 384–386.
2. A. Fiat and A. Shamir, How to prove yourself: Practical solutions to identification and signature problems, Proceedings of Crypto 86, Santa-Barbara (1986), 181–187.
3. S. Harari, This volume.