%% You should probably cite draft-ietf-jcardcal-jcard instead of this I-D.
@techreport{kewisch-vcard-in-json-01,
    number =    {draft-kewisch-vcard-in-json-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-kewisch-vcard-in-json/01/},
    author =    {Philipp Kewisch},
    title =     {{jCard: The JSON format for vCard}},
    pagetotal = 23,
    year =      2013,
    month =     mar,
    day =       18,
    abstract =  {This specification defines "jCard", a JSON format for vCard data.},
}