Badawi, A., and A. Nasrulloh. “Effect of Circuit and Interval Training Methods on the Agility and VO₂max of Porprov Football Players in Pati Regency in Terms of Leg Muscle Endurance”. Physical Education Theory and Methodology, vol. 23, no. 4, Aug. 2023, pp. 499-04, doi:10.17309/tmfv.2023.4.02.