1. Kong D, Gray D, Tao H. Counting pedestrians in crowds using viewpoint invariant training. In: Proceedings of British Machine Vision Conference. 2005
2. Lin S F, Chen J Y, Chao H X. Estimation of number of people in crowded scenes using perspective transformation. IEEE Transactions on Systems, Man, and Cybernetics-Part A: Systems and Humans, 2001, 31(6): 645–654
3. Reisman P, Mano O, Avidan S, Shashua A. Crowd detection in video sequences. In: Proceedings of IEEE Intelligent Vehicles Symposium. 2004, 66–71
4. Huang X Y, Li L Y, Sim T. Stereo-based human head detection from crowd scenes. In: Proceedings of International Conference on Image Processing. 2004, 1353–1356
5. Mckenna S J, Jabri S, Duric Z, Rosenfeld A, Wechsler H. Tracking groups of people. Computer Vision and Image Understanding, 2000, 80(1): 42–56