Sami Yousif , Faris, et al. “Constructing and Standardizing A Test For Measuring Legs’ Vertical Strength Defined by Speed in Youth Basketball”. Journal of Physical Education, vol. 24, no. 3, Sept. 2012, p. 21, https://www.jcope.uobaghdad.edu.iq/index.php/jcope/article/view/1745.