%% You should probably cite rfc7529 instead of this I-D.
@techreport{ietf-calext-rscale-03,
    number =    {draft-ietf-calext-rscale-03},
    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/03/},
    author =    {Cyrus Daboo and Gregory Yakushev},
    title =     {{Non-Gregorian Recurrence Rules in iCalendar}},
    pagetotal = 19,
    year =      2015,
    month =     jan,
    day =       7,
    abstract =  {This document defines extensions to iCalendar (RFC 5545) to support use of non-Gregorian recurrence rules. It also defines how CalDAV (RFC 4791) servers and clients can be extended to support these new recurrence rules.},
}