1. The expression of emotions in man and animals;Darwin,1872
2. Duplication of facial expression: Conditions affecting task and possible clinical usefulness;Draughton;Journal of Personality,1973
3. Unmasking the face;Ekman,1975
4. Pictures of facial affect;Ekman,1976
5. Facial action coding system (FACS): A technique for the measurement of facial action;Ekman,1978