On commutativity of rings with constraints on subsets H. A. S. Abujabal; M. A. Khan; M. S. Khan; Mohammad S. Samman — 1993 Czechoslovak Mathematical Journal
On annihilators of BCK-algebras H. A. S. Abujabal; M. A. Obaid; M. Aslam; Allah-Bakhsh Thaheem — 1995 Czechoslovak Mathematical Journal