Krawczyk, M.; Pociecha, M. INFLUENCE OF A 6-WEEK MIXED BALLISTIC-PLYOMETRIC TRAINING ON THE LEVEL OF SELECTED STRENGTH AND SPEED INDICES OF THE LOWER LIMBS IN YOUNG FOOTBALL PLAYERS. SIE 2019, 4, 198-206. https://doi.org/10.17770/sie2019vol4.3718.