ACTA MATHEMATICA HUNGARICA, cilt.87, ss.33-45, 2000 (SCI-Expanded)
We define two closure operators of some well-known topological categories and investigate the relationships between these closure operators and the one that is given in [9]. As a consequence, we characterize separation properties To, T-1, and T-2 for these well-known categories and compare them with the ones that are given in [3] and [6]. Finally, we characterize the epimorphisms in the subcategories of these given categories.