*Definition [#v25671cd]
-A bitopological space (X, τ, μ) is said to be pairwise Hausdorff if , for each two distinct points x and y, there are a τ-neighbourhood U of x and a μ-neighbourhood V of y such that U ∩ V = &ref(http://www.eaflux.com/imgtex/imgtex.fcgi?%5bres=100%5d%7b%5c%5b%20%5cemptyset%20%5c%5d%7d%25.png);.

*Reference [#w7c148be]
-Kelly, J. C.,''Bitopological spaces.'',Proc. London Math. Soc. (3) 13 1963 71–89.