Grad, Rafał, and Kazimierz Kochanowicz. “The Quality of Landing in the Gymnastic Exercises, As Seen by Coaches in Acrobatic Gymnastics and Tumbling”. Journal of Education, Health and Sport, vol. 7, no. 6, June 2017, pp. 190-0, https://apcz.umk.pl/JEHS/article/view/4520.