RFCs:

[RFC 3779] X.509 Extensions for IP Addresses and AS Identifiers.

[RFC 4301] Security Architecture for the Internet Protocol.

Publications:

Kent, Stephen; Lynn, Charles, Jr; Mikkelsen, Jan; Seo, Karen.
Secure Border Gateway Protocol (S-BGP).
February 2000. Proceedings of ISOC Network and Distributed Systems Security Symposium, Internet Society, Reston, VA.

Kent, Stephen; Lynn, Charles, Jr; Seo, Karen.
Secure Border Gateway Protocol (Secure-BGP).
April 2000. IEEE Journal on Selected Areas in Communications Vol. 18, No. 4, pp. 582 - 592.