[1] draft-mutz-http-attributes-00 - User-Agent Display Attributes (2014-10-12 17:03:29 +09:00 版) <https://tools.ietf.org/html/draft-mutz-http-attributes-00>

[2] RFC 4229 - HTTP Header Field Registrations (2014-11-02 18:53:20 +09:00 版) <http://tools.ietf.org/html/rfc4229#section-2.2.13>