%% You should probably cite rfc1766 instead of this I-D.
@techreport{ietf-mailext-lang-tag-01,
    number =    {draft-ietf-mailext-lang-tag-01},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-mailext-lang-tag/01/},
    author =    {Harald T. Alvestrand},
    title =     {{Tags for the Identification of Languages}},
    pagetotal = 9,
    year =      1994,
    month =     dec,
    day =       13,
    abstract =  {This document describes a language tag for use in cases where it is desired to indicate the language used in an information object. {[}STANDARDS-TRACK{]}},
}