%% You should probably cite rfc7114 instead of this I-D.
@techreport{leiba-smime-type-registry-02,
    number =    {draft-leiba-smime-type-registry-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-leiba-smime-type-registry/02/},
    author =    {Barry Leiba},
    title =     {{Creation of a Registry for smime-type Parameter Values}},
    pagetotal = 4,
    year =      2013,
    month =     nov,
    day =       12,
    abstract =  {Secure/Multipurpose Internet Mail Extensions (S/MIME) defined the Content-Type parameter "smime-type". As the list of defined values for that parameter has increased, it has become clear that a registry is needed to document these values. This document creates the registry, registers the current values, and specifies the policies for registration of new values.},
}