@misc{rfc4021,
    series =    {Request for Comments},
    number =    4021,
    howpublished =  {RFC 4021},
    publisher = {RFC Editor},
    doi =       {10.17487/RFC4021},
    url =       {https://www.rfc-editor.org/info/rfc4021},
    author =    {Graham Klyne and Jacob Palme},
    title =     {{Registration of Mail and MIME Header Fields}},
    pagetotal = 54,
    year =      2005,
    month =     mar,
    abstract =  {This document defines the initial IANA registration for permanent mail and MIME message header fields, per RFC 3864. {[}STANDARDS-TRACK{]}},
}