(Λ,sδ)-open

Definition

• A subset of a topological space (X,τ) is called (Λ,sδ)-open if X ∖ A is (Λ,sδ)-closed.

Reference

• 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.