Atabekyan, V.S., et al. “ANALOGUES OF NIELSEN’S AND MAGNUS’S THEOREMS FOR FREE BURNSIDE GROUPS OF PERIOD 3”. Proceedings of the YSU A: Physical and Mathematical Sciences, vol. 51, no. 3 (244), Dec. 2017, pp. 217-23, doi:10.46991/PYSU:A/2017.51.3.217.