1. AIM USA-1994, Uniform Symbology Specification PDF417.
2. ANSI/AIM BC11-1997, International Symbology Specification-Data Matrix.
3. ANSI X9.30, Public Key Cryptography for the Financial Services Industry: Part I: The Digital Signature Algorithm (DSA) (Revised), draft, July 1999.
4. ANSI X9.62, Public-key Cryptography for the Financial Services Industry: The Elliptic Curve Digital Signature Algorithm (ECDSA), 1999.
5. T. Biasi, R. Cordery, S. Joshi and L. Pintsov, “Digital postage mark verification”, Proceedings of International Conference on Mail Technology-Tomorrow’s World, Brighton, UK, 1999, pp. 199–211, published by Professional Engineering Publishing Ltd, for the Institution of Mechanical Engineers, Bury St Edmunds and London, UK 1999.