1. Velicko N., “H-closed topological spaces” Math. Sb., Vol. 70, No. 112, 1966, pp. 103–118.
2. Saleh M., “On ϑ-continuity and strong ϑ-continuity”, Applied Mathematics E-Notes., Vol. 3, 2003, pp. 42–48.
3. Calads M., “Some properties of ϑ-open sets”, Divulgations Math., Vol. 12, No. 2, 2004, pp. 161–169.
4. Saleh M., “On ϑ-closed sets and some forms of continuity”, Archivum Mathematics, Tomus, Vol. 40, 2004, pp. 383–393.
5. On functionally θ-normal spaces