The publisher, in agreement with the Editor-in-Chief, has retracted this article because it contains large portions of text that have been duplicated from a previously published article: Wang Z, Wang S, Ji Q (2013) Capturing complex spatio-temporal relations among facial muscles for facial expression recognition. Proc. IEEE Conference Computer Vision Pattern Recognition 3422-3429.

The online version of this article contains the full text of the retracted article as electronic supplementary material.