Bordbar, Hashem, Mohammad Mehdi Zahedi, and Young Bae Jun. “Internal and External Cubic Subalgebras of BCK/BCI-Algebras”. Journal of the Indonesian Mathematical Society 27, no. 1 (March 31, 2021): 48–63. Accessed May 3, 2024. https://jims-a.org/index.php/jimsa/article/view/968.