%% You should probably cite rfc7529 instead of this I-D.
@techreport{ietf-calext-rscale-02,
    number =    {draft-ietf-calext-rscale-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-ietf-calext-rscale/02/},
    author =    {Cyrus Daboo and Gregory Yakushev},
    title =     {{Non-Gregorian Recurrence Rules in iCalendar}},
    pagetotal = 18,
    year =      2014,
    month =     dec,
    day =       10,
    abstract =  {This document defines how non-Gregorian recurrence rules can be specified and used in iCalendar data, and with CalDAV servers.},
}