Nitit, Fransiskus Saferius, et al. “Application of Service Duel Approach to Improve High Secondary School Students’ Badminton Backhand Serve Accuracy ”. ETDC: Indonesian Journal of Research and Educational Review , vol. 6, no. 1, Sept. 2026, pp. 294-0, doi:10.51574/ijrer.v6i1.5179.