Definition
- In a topological space (X,τ) an open cover of (X,τ) is T_3-open if for every set U in there exist open sets V and W such that .
Reference
- Przemski, M., Nearly T_i-continuous functions and some separation axioms. (Serbo-Croatian summary), Glas. Mat. Ser. III 21(41) (1986), no. 2, 431–435.