L. Nacke, S. Stellmach, D. Sasse, and C. Lindley. Proceedings of the 5th Conference on Communication by Gaze Interaction – COGAIN 2009: Gaze Interaction For Those Who Want It Most, page 49-54. Lyngby, Denmark, The COGAIN Association, The COGAIN Association, (2009)available online.
S. Vickers, H. Istance, A. Hyrskykari, N. Ali, and R. Bates. Proceedings of the 7th International conference on disability, virtual reality and associated technologies: ICDVRAT 2008, (September 2008)