Florian Metze Zaid Sheikh Alex Waibel Jonas Gehring Kevin Kilgour Quoc Bao Nguyen Van Huy Nguyen Models of tone for tonal and non-tonal languages. 261-266 2013 ASRU https://doi.org/10.1109/ASRU.2013.6707740 conf/asru/2013 db/conf/asru/asru2013.html#MetzeSWGKNN13