Persulessy, Elvinus. “KONSEP DASAR SEMIGRUP REGULER REDUKTIF”. BAREKENG: Jurnal Ilmu Matematika dan Terapan 1, no. 1 (March 1, 2007): 9-11. Accessed April 20, 2024. https://ojs3.unpatti.ac.id/index.php/barekeng/article/view/216.