@patent{Black:USPTO:1995a,
  title = {Apparatus and method for tracking facial motion through a sequence of images},
  howpublished = {US Pat. 5,802,220},
  month = dec,
  year = {1995},
  slug = {black-uspto-1995a},
  author = {Black, M. J. and Yacoob, Y.},
  month_numeric = {12}
}