Acknowledgements
Costas Stratelos     Xavier Brolly
Brolly, Stratelos & Mulligan (2003), "Model-based head pose estimation for air-traffic controllers," Proc. Intl. Conf. Image Processing (ICIP).     Brolly & Mulligan (2004), "Implicit calibration of a remote gaze tracker," CVPR Workshop on Object Tracking Beyond the Visible Spectrum.