Neiberg, Daniel, and Joakim Gustafson, “Cues to Perceived Functions of Acted and Spontaneous Feedback Expressions”, Proceedings of the Interdisciplinary Workshop on Feedback Behaviors in Dialog, September 7–8, 2012, Stevenson, WA, pp. 53–56, http://www.cs.utep.edu/nigel/feedback/proceedings/full-proceedings.pdf.
