Last-modified: 2011-04-16 (土) 15:23:25
- Let (X,τ) be a topological space, A subset A of a space S is called a Λ^s_δ-D set if there are two (Λ,sδ)-open sets U and V in X such that U≠X and A=U-V.
- Caldas, M.; Ganster, M.; Georgiou, D. N.; Jafari, S.; Moshokoa, S. P., δ-semiopen sets in topology. (English summary), Proceedings of the 19th Summer Conference on Topology and its Applications., Topology Proc. 29 (2005), no. 2, 369–383.