V. V. Khrenkova - Senior Research Scientist, Southern Federal University (Rostov-on-Don). E-mail: vvkhrenkova@gmail.com
V. V. Zolotukhin - Senior Research Scientist, Southern Federal University (Rostov-on-Don). E-mail: zokhr_100@mail.ru
P. V. Zolotukhin - Post-graduate Student, Southern Federal University (Rostov-on-Don). E-mail: p.zolotukhin@gmail.com