[1] draft-ietf-http-options-02 - Specification of HTTP/1.1 OPTIONS messages (2014-10-17 22:55:52 +09:00 版) https://tools.ietf.org/html/draft-ietf-http-options-02#section-3.4

[2] RFC 4229 - HTTP Header Field Registrations ( (2014-11-02 18:53:20 +09:00 版)) http://tools.ietf.org/html/rfc4229#section-2.2.1