Aoyagi, Kenryu, Kaori Ishii, Ai Shibata, Hirokazu Arai, and Koichiro Oka. 2015. “Expected Qualifications for External Coaches in School-Based Extracurricular Sports Activities”. Journal of Educational and Social Research 5 (3). London, U.K.:53. https://www.richtmann.org/journal/index.php/jesr/article/view/7699.