%% You should probably cite draft-ietf-httpbis-immutable instead of this I-D.
@techreport{mcmanus-immutable-01,
    number =    {draft-mcmanus-immutable-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-mcmanus-immutable/01/},
    author =    {Patrick McManus},
    title =     {{HTTP Immutable Responses}},
    pagetotal = 5,
    year =      2016,
    month =     dec,
    day =       19,
    abstract =  {The immutable HTTP response Cache-Control extension allows servers to identify resources that will not be updated during their freshness lifetime. This assures that a client never needs to revalidate a cached fresh resource to be certain it has not been modified.},
}