[1] X. Sun, F. Su, and A. Cai, Acta Opt. Sin. (in Chinese) 11, 2083 (2008).

[2] J. Yang, W. Lu, and A. Waibel, Skin-Color Modeling and Adaptation (Springer, Berlin, 1997).

[3] S. J. McKenna, S. Gong, and Y. Raja, Pattern Recogn. 31, 1883 (1998).

[4] K. Sobottka and I. Pitas, in Proceedings of International Conference on Pattern Recognition 3, 421 (1996).

[5] C. Kim, B.-J. You, M.-H. Jeong, and H. Kim, Pattern Recogn. 41, 22 (2008).

[6] D. Chai and K. N. Ngan, in Proceedings of Third International Conference on Automatic Face and Gesture Recognition 124 (1998).

[7] Y. Dai and Y. Nakano, Pattern Recogn. 29, 1007 (1996).

[8] E. Saber and A. M. Tekalp, Pattern Recogn. Lett. 8, 669 (1998).

[9] K.-M. Cho, J.-H. Jang, and K.-S. Hong, Pattern Recogn. 34, 1067 (2001).

[10] M. Soriano, B. Martinkauppi, S. Huovinen, and M. Laaksonen, Pattern Recogn. 36, 681 (2003).

[11] S. K. Naik and C. A. Murthy, IEEE Trans. Image Process. 9, 505 (2000).

[12] C. C. Yang and J. J. Rodriguez, in Proceedings of IEEE International Conference on Systems, Man, and Cybernetics 1, 667 (1995).