@Article{GeBeKr01,
  author =  "Georghiades, A.S. and Belhumeur, P.N. and Kriegman, D.J.",
  title =   "From Few to Many: Illumination Cone Models for Face Recognition under
               Variable Lighting and Pose",
  journal = "IEEE Trans. Pattern Anal. Mach. Intelligence",
  year =  2001,
  volume = 23,
  number = 6,
  pages= "643-660"}