Muhammad Q. Jameel Ahmed. The effectiveness of the two fields of learning in the two styles of self - group competition and their impact on learning the skills of the ace serve and defending the court in volleyball. qjpes [Internet]. 2024 Mar. 27 [cited 2024 May 17];24(1):88-95. Available from: http://spojou.qu.edu.iq/index.php/qjpes/article/view/96