@unpublished{ChenLiXu2009,
  author  = {Hua Chen and Wei-Xi Li and Chao-Jiang Xu},
  title   = {Gevrey hypoellipticity for linear and non-linear Fokker-Planck equations},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(2007) 07},
  year    = {2009},
}