Last-modified: 2012-10-04 (木) 14:33:55
- A topological space (X,τ) is said to be pre-R_0 if every pre-open? set contains the pre-closure? of each of its singletons.
- Caldas, M.; Georgiou, D. N.; Jafari, S. , Characterizations of low separation axioms via α-open sets and α-closure operator., (English summary) Bol. Soc. Parana. Mat. (3) 21 (2003), no. 1-2, 97–111.