L. Rozo, S. Calinon, and D. Caldwell. Robot and Human Interactive Communication, 2014 RO-MAN: The 23rd IEEE International Symposium on, page 619--624. IEEE, (2014)
J. Parker, A. Khoogar, and D. Goldberg. Robotics and Automation, 1989. Proceedings., 1989 IEEE International Conference on, page 271--276. IEEE, (1989)