1. Audacity Team 2013 Audacity ® software, version 2.0.3 http://audacity.sourceforge.net/
2. Bates , D. Maechler , M. Bolker , B. Walker , S 2015 Lme4: linear mixed-effects models using eigen and S4, R package version 1.1-9 https://CRAN.R-project.org/package=lme4
3. A Generalization of the Method of m Rankings
4. Boersma , P. Weenink , D 2011 Praat: doing phonetics by computer, version 5.3 http://www.praat.org/