1. Kohnfelder L.: ‘Towards a practical public‐key cryptosystem’.Bachelor's thesis Massachusetts Institute of Technology 1978
2. China Electronic signature law 2004
3. Asia‐Pacific Economic Cooperation: ‘Guidelines for schemes to issue certificates capable of being used in cross jurisdiction e‐commerce’ 2004
4. European Telecommunications Standards Institute: ‘Policy requirements for certification authorities issuing qualified certificates’ 2000
5. European Union: ‘Directive on a community framework for electronic signatures’ 1999