Simon Lucey Sridha Sridharan Vinod Chandran An investigation of HMM classifier combination strategies for improved audio-visual speech recognition. 1185-1188 2001 INTERSPEECH https://doi.org/10.21437/Eurospeech.2001-309 conf/interspeech/2001 db/conf/interspeech/interspeech2001.html#LuceySC01