%% You should probably cite draft-ietf-core-multipart-ct instead of this I-D.
@techreport{bormann-core-maybe-00,
    number =    {draft-bormann-core-maybe-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-bormann-core-maybe/00/},
    author =    {Carsten Bormann},
    title =     {{The application/maybe media type}},
    pagetotal = 6,
    year =      2018,
    month =     mar,
    day =       18,
    abstract =  {Many media types may be used in situations where it may beneficial to indicate that the object represented in this media type is not yet (or no longer) present. The Observe option introduced in Observing Resources in the Constrained Application Protocol (CoAP) (RFC7641) requires sequences of responses (notifications) to carry the same Content-Format. The application/maybe media type provides a way to use a single media type (and thus Content-Format) to express presence or absence of information in a specific media type.},
}