[
Ekman, P. and Friesen, W. (1978): Facial Action Coding System: A Technique for the Measurement of Facial Movement. Palo Alto: Consulting Psychologists Press.10.1037/t27734-000
]Search in Google Scholar
[
Scherer, K. (2005): “What Are Emotions? And How Can They Be Measured?” Social Science Information, Vol. 44, No. 4, pp. 695 - 729.
]Search in Google Scholar
[
Garbas, J.-U.; Ruf, T.; Unfried, M. and Dieckmann, A. (2013): Towards Robust Real-time Valence Recognition from Facial Expressions for Market Research Applications. Proceedings of the 5th International Conference on Affective Computing and Intelligent Interaction, pp. 570 - 575.10.1109/ACII.2013.100
]Search in Google Scholar