1. Ross Anderson: Why Cryptosystems Fail; 1st ACM Conference on Computer and Communications Security, acm Press, New York 1993, 215–227.
2. Peter Bauer, Heribert Peuckert: Chipkarten mit Kryptographie erschließen neue Anwendungsfelder; Siemens-Zeitschrift Special, FuE, Frühjahr 1994, 17–20.
3. Jean-Paul Boly, Antoon Bosselaers, Ronald Cramer, Rolf Michelsen, Stig Mjølsnes, Frank Muller, Torben Pedersen, Birgit Pfitzmann, Peter de Rooij, Berry Schoenmakers, Matthias Schunter, Luc Vallée, Michael Waidner: Digital Payment Systems in the ESPRIT Project CAFE; Proc. of Securicom '94, Paris, June 1994.
4. Jurjen Bos, David Chaum: SmartCash: a Practical Electronic Payment System; Centrum voor Wiskunde en Informatica, Computer Science/Departement of Algorithmics and Architecture, Report CS-R9035, August 1990.
5. Stefan Brands: An Efficient Off-line Electronic Cash System Based On The Representation Problem; Centrum voor Wiskunde en Informatica, Computer Science/Departement of Algorithmics and Architecture, Report CS-R9323, March 1993.