DerechV. D. “Characterization of the Semilattice of Idempotents of a Finite-Rank Permutable Inverse Semigroup With Zero”. Ukrains’kyi Matematychnyi Zhurnal 59, no. 10 (October 25, 2007): 1353–1362. Accessed November 22, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/3394.