Definition
- Let S be a subset of a topological space (X, τ). The set of all λ-cluster points of S is called the λ-closure of S and is denoted by .
Reference
- Caldas Miguel, Jafari Saeid, On some low separation axioms via λ-open and λ-closure operator., Rend. Circ. Mat. Palermo (2) 54 (2005), no. 2, 195–208.