A. Damasio, D. Tranel, and H. Damasio. chapter Somatic markers and the guidance of behaviour: theory and preliminary
testing, page 217-229. New York: Oxford University Press, (1991)
M. Bosjnak, and T. Tuten. Journal of Computer Mediated Communication, (2001)3 non response types differenciated - complete (all), unit (complete
loss of answers).