@article{liu2015main,
  title={A main directional mean optical flow feature for spontaneous micro-expression recognition},
  author={Liu, Yong-Jin and Zhang, Jin-Kai and Yan, Wen-Jing and Wang, Su-Jing and Zhao, Guoying and Fu, Xiaolan},
  journal={IEEE Transactions on Affective Computing},
  volume={7},
  number={4},
  pages={299--310},
  year={2015},
  publisher={IEEE}
}