*Definition [#n46675f6]
-A topological space (X,τ) is a T_-1 space if for arbitrary three distinct points of X, one of them is [[weakly separated]] from one of the two other points.

*Property [#edf7d7fc]
-T_-1 ⇒ [[S_R]].

*Reference [#de97d01d]
-Guia, Josep ''The Sα separation axioms.'', (Serbo-Croatian summary),  Mat. Vesnik 38 (1986), no. 1, 45–57.