%% You should probably cite draft-ietf-httpbis-variants instead of this I-D.
@techreport{nottingham-variants-00,
    number =    {draft-nottingham-variants-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-nottingham-variants/00/},
    author =    {Mark Nottingham},
    title =     {{HTTP Variants}},
    pagetotal = 13,
    year =      2017,
    month =     sep,
    day =       28,
    abstract =  {This specification introduces the HTTP "Variants" response header field to communicate what representations are available for a given resource.},
}