Christian Plahl Ralf Schlüter Hermann Ney Hierarchical bottle neck features for LVCSR. 1197-1200 2010 INTERSPEECH http://www.isca-speech.org/archive/interspeech_2010/i10_1197.html conf/interspeech/2010 db/conf/interspeech/interspeech2010.html#PlahlSN10