%% You should probably cite rfc5845 instead of this I-D.
@techreport{ietf-netlmm-grekey-option-09,
    number =    {draft-ietf-netlmm-grekey-option-09},
    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-netlmm-grekey-option/09/},
    author =    {Kent Leung and Mohamed Khalil and Sri Gundavelli and Ahmad Muhanna},
    title =     {{Generic Routing Encapsulation (GRE) Key Option for Proxy Mobile IPv6}},
    pagetotal = 25,
    year =      2009,
    month =     may,
    day =       5,
    abstract =  {This specification defines a new mobility option for allowing the mobile access gateway and the local mobility anchor to negotiate Generic Routing Encapsulation (GRE) encapsulation mode and exchange the downlink and uplink GRE keys that are used for marking the downlink and uplink traffic that belong to a specific mobility session. In addition, the same mobility option can be used to negotiate the GRE encapsulation mode without exchanging the GRE keys. {[}STANDARDS-TRACK{]}},
}