Simonian, I. R. “VARIETIES OF SOLID DISTRIBUTIVE SEMIGROUPS”. Proceedings of the YSU A: Physical and Mathematical Sciences 34, no. 2 (193) (October 13, 2000): 117–119. Accessed June 12, 2026. https://journals.ysu.am/proceedings-phys-math/article/view/vol34_no2_2000_pp117-119.