%% You should probably cite draft-ietf-calext-icalendar-series instead of this I-D.
@techreport{douglass-icalendar-series-00,
    number =    {draft-douglass-icalendar-series-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-douglass-icalendar-series/00/},
    author =    {Michael Douglass},
    title =     {{Support for Series in iCalendar}},
    pagetotal = 26,
    year =      2017,
    month =     feb,
    day =       15,
    abstract =  {This specification updates {[}RFC5545{]} by defining a new repeating set of events known as a series. This differs from recurrences in that each instance is a separate entity with a parent relationship to a specified template entity.},
}