Ruch, Willibald Friedrich, Jennifer Hofmann, and Tracey Platt. “Investigating Facial Features of Four Types of Laughter in Historic Illustrations”. The European Journal of Humour Research 1, no. 1 (March 31, 2013): 99–118. Accessed April 16, 2024. https://ww.europeanjournalofhumour.org/ejhr/article/view/Willibald%20Ruch%20et%20al.