ABUJABAL, H. A. S. “A GENERALIZATION OF SOME COMMUTATIVITY THEOREMS FOR RINGS I”. Tamkang Journal of Mathematics 21, no. 3 (September 1, 1990): 239–245. Accessed May 3, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4669.