T. Rupp, N. Karajan, W. Ehlers, and S. Schmitt. Proceedings of the XXIIIrd Congress of the International Society of Biomechanics, Brussels, Belgium, (2011)
M. Wu, J. Han, O. Röhrle, W. Thorpe, and P. Nielsen. 11th Australian International Conference on Speech Science & Technology, page 354--359. University of Auckland New Zealand, (2006)