Sơn, Nguyễn Hoài, et al. “New PWM Switching Techniques for an Optimum Cascade 3 3 NPC Inverter Operation”. <i>Journal of Computer Science and Cybernetics</i>, vol. 28, no. 1, June 2012, pp. 22-31, doi:10.15625/1813-9663/28/1/1062.