*Definition [#fb238d48]
-An operation γ on a topology τ on X is a mapping γ: τ → P(X), such that &ref(http://www.eaflux.com/imgtex/imgtex.fcgi?%5bres=100%5d%7b%5c%5b%20V%5csubset%20V%5e%5cgamma%20%5c%5d%7d%25.png); for each V ∈ τ, where P(X) is the power set of X and &ref(http://www.eaflux.com/imgtex/imgtex.fcgi?%5bres=100%5d%7b%5c%5b%20V%5e%5cgamma%20%5c%5d%7d%25.png); denotes the value of γ at V .

*Reference [#rbd79a56]
-Basu, C. K.; Afsan, B. M. Uzzal; Ghosh, M. K., ''A class of functions and separation axioms with respect to an operation.'' (English summary), Hacet. J. Math. Stat. 38 (2009), no. 2, 103-118.