%% You should probably cite rfc7636 instead of this I-D.
@techreport{ietf-oauth-spop-00,
    number =    {draft-ietf-oauth-spop-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-ietf-oauth-spop/00/},
    author =    {Nat Sakimura and John Bradley and Naveen Agarwal},
    title =     {{Symmetric Proof of Possession for the OAuth Authorization Code Grant}},
    pagetotal = 8,
    year =      2014,
    month =     aug,
    day =       26,
    abstract =  {The OAuth 2.0 public client utilizing authorization code grant is susceptible to the code interception attack. This specification describe a mechanism that acts as a control against this threat.},
}