Ursaru, O., and C. Aghion. “Multilevel Inverters With Imbricated Switching Cells, PWM and DPWM-Controlled”.
Elektronika Ir Elektrotechnika
, vol. 104, no. 8, Oct. 2010, pp. 23-26, https://eejournal.ktu.lt/index.php/elt/article/view/9202.