1. Cartan, H., “Theorie des filters”, C.R. Acad. Sc. Paris, 205: 595-598, (1937).
2. Cartan, H., “Filtres et ultrafiltres”, C.R. Acad. Sc. Paris, 205: 777–779, (1937).
3. Connections between convergence and nearness
4. Baran, M., “Separation properties”, Indian J. Pure Appl. Math. 23: 333-341, (1991).
5. Baran, M., “The Notion of Closedness in Topological Categories”, Comment. Math. Univ. Carolinae 34: 383-395, (1993).