@article{lee2013syntactic,
  title={A syntactic approach to robot imitation learning using probabilistic activity grammars},
  author={Lee, Kyuhwa and Su, Yanyu and Kim, Tae-Kyun and Demiris, Yiannis},
  journal={Robotics and Autonomous Systems},
  volume={61},
  number={12},
  pages={1323--1334},
  year={2013},
  publisher={Elsevier}
}