Pruekpramool, Chaninan, Nattika Jaroentaku, and Siwachoat Srisuttiyakorn. 2020. “Efficiency of Pearson, Spearman and Kendall’s Correlation Coefficients When Data Is Non-Normal Distributed”. An Online Journal of Education 15 (2):OJED1502040 (16 pages). https://so01.tci-thaijo.org/index.php/OJED/article/view/245395.