@article{JASON2003ACTIVE,
  title={ACTIVE HEAD TRACKING BASED ON CHROMATIC SHAPE FITTING},
  author={JASON Z.  ZHANG and Q. M. JONATHAN  WU and WILLIAM A.  GRUVER},
  journal={International Journal of Pattern Recognition & Artificial Intelligence},
  volume={17},
  number={04},
  pages={529-544},
  year={2003},
}