Tet Fei Yap Eliathamby Ambikairajah Julien Epps Eric H. C. Choi Cognitive load classification using formant features. 221-224 2010 ISSPA http://dx.doi.org/10.1109/ISSPA.2010.5605535 conf/isspa/2010 db/conf/isspa/isspa2010.html#YapAEC10