Team, S. “The Order of Elements of the Semigroups $(W_{\tau}(X_2))^2$ and $(W_{\tau}(X_3))^3$: Damrongsak Punyathip, Thawhat Changphas”. Thai Journal of Mathematics, vol. 15, no. 1, Apr. 2017, pp. 121-3, https://thaijmath2.in.cmu.ac.th/index.php/thaijmath/article/view/670.