How do Leaders Perceive Stress and Followership from Nonverbal Behaviors Displayed by Virtual Followers? - Guillaume Demary; Jean-Claude Martin; Stéphane Dubourdieu; Stéphane Travers; Virginie Demulier (Proceedings of the 19th ACM International Conference on Intelligent Virtual Agents, IVA 2019, Paris, France, July 2-5, 2019, 2019)