%% You should probably cite draft-ietf-httpbis-variants instead of this I-D.
@techreport{nottingham-variants-02,
    number =    {draft-nottingham-variants-02},
    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/02/},
    author =    {Mark Nottingham},
    title =     {{HTTP Representation Variants}},
    pagetotal = 19,
    year =      2018,
    month =     feb,
    day =       12,
    abstract =  {This specification introduces an alternative way to communicate a secondary cache key for a HTTP resource, using the HTTP "Variants" and "Variant-Key" response header fields. Its aim is to make HTTP proactive content negotiation more cache-friendly.},
}