@Misc{ 
  CanFlo11,
  author = { Cannarsa, Piermarco and Floridia, Giuseppe },
  title = { Approximate controllability for linear degenerate parabolic problems
  with bilinear control },
  journal = {  },
  year = { 2011 },
  pages = {  },
  URL = { http://cvgmt.sns.it/paper/3693/ },
  note = { cvgmt preprint}
}