1. Abd El-Aziz Ahmed Abo-Khadra, On generalized forms of compactness, Master’s Thesis, Faculty of Science, Tanta University, Egypt (1989).
2. M. E. Abd El-Monsef, S. N. El-Deeb and R. A. Mahmoud, $${\beta}$$ β -open sets and $${\beta\mbox{-}}$$ β - continuous mappings, Bull. Fac. Sci. Assiut. Univ., 12 (1983), 77–90.
3. Andrijević D.: Semi-preopen sets. Mat. Vesnik, 38, 24–32 (1986)
4. D. Andrijević, On b-open sets, Mat. Vesnik, 48 (1996), 59–64.
5. D. E. Cameron, Properties of S-closed spaces, Proc. Amer. Math. Soc., 72 (1978), 581–586.