R-fuzzy Strongly Preopen Sets in Fuzzy Topological Spaces Y.C. Kim; A.A. Ramadan; S.E. Abbas — 2003 Matematički Vesnik
Compactness in intuitionistic fuzzy topological spaces. Ramadan, A.A.; Abbas, S.E.; Abd El-Latif, A.A. — 2005 International Journal of Mathematics and Mathematical Sciences