Lutkova N.V., Makarov Yu.M., Lutkov V.F., and Dakshevich N.V. “Innovative Aspects of Varieties of Serve in Modern men’s Volleyball”. Theory and Practice of Physical Culture, no. 7, Aug. 2024, pp. 6-8, http://tpfk.ru/index.php/TPPC/article/view/1061.