Singh, S. The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography. Anchor, 2000, 432 pp.
ISBN 978-0385495325
Mason, S. Electronic Signatures in Law. 3rd ed. Cambridge University Press, 2012, 408 pp.
ISBN 978-1107012295
REGULATION (EU) No 910/2014 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL (EU) 910/2014 of 23 July 2014 on electronic identification and trust services for electronic transactions in the internal market and repealing Directive 1999/93/EC