%% You should probably cite rfc2156 instead of this I-D.
@techreport{kille-mixer-rfc1327bis-04,
    number =    {draft-kille-mixer-rfc1327bis-04},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-kille-mixer-rfc1327bis/04/},
    author =    {Steve Kille},
    title =     {{MIXER (Mime Internet X.400 Enhanced Relay): Mapping between X.400 and RFC 822/MIME}},
    pagetotal = 144,
    year =      1997,
    month =     feb,
    day =       23,
    abstract =  {This document relates primarily to the ITU-T 1988 and 1992 X.400 Series Recommendations / ISO IEC 10021 International Standard. This ISO/ITU-T standard is referred to in this document as "X.400", which is a convenient shorthand. {[}STANDARDS-TRACK{]}},
}