YEN, CHEN-TE. “RINGS WITH $(R,R,R)$ AND $((R,R,R),R)$ IN THE LEFT NUCLEUS”. Tamkang Journal of Mathematics 24, no. 2 (June 1, 1993): 209–213. Accessed April 23, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4491.