6.1. 规范性参考文献 (Normative References)

[RFC2119] Bradner, S., "用于在 RFC 中指示要求级别的关键词 (Key words for use in RFCs to Indicate Requirement Levels)", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "超文本传输协议 -- HTTP/1.1 (Hypertext Transfer Protocol -- HTTP/1.1)", RFC 2616, June 1999.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "消息 Header Field 的注册程序 (Registration Procedures for Message Header Fields)", BCP 90, RFC 3864, September 2004.

6.1. 规范性参考文献 (Normative References)​