Homologation of the Olympic ski stadiums as the basis for the requirements for the technical, tactical and functional training of cross country athletes - Khmelnytska, Y.; Kropta, R.; Hruzevych, I.; Kormiltsev, V.; Yefanova, V.; Smirnova, Z.; Tron, R.; Hudzevych, L. (Journal of Physical Education and Sport, 2020)