<hi xmlns="http://www.tei-c.org/ns/1.0" rend="bold">Ekman, Paul / Friesen, Wallace V. (1978)</hi>: <hi xmlns="http://www.tei-c.org/ns/1.0" rend="italic">The Facial Action Coding System: A Technique for the Measurement of Facial Movement</hi>. Palo Alto: Consulting.