%% You should probably cite rfc8607 instead of this I-D.
@techreport{ietf-calext-caldav-attachments-02,
    number =    {draft-ietf-calext-caldav-attachments-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-caldav-attachments/02/},
    author =    {Cyrus Daboo and Arnaud Quillaud and Kenneth Murchison},
    title =     {{CalDAV Managed Attachments}},
    pagetotal = 33,
    year =      2017,
    month =     mar,
    day =       13,
    abstract =  {This specification defines an extension to the calendar access protocol (CalDAV) to allow attachments associated with iCalendar data to be stored and managed on the server.},
}