Some authors use f ∘ g : X → Z, defined by (f ∘ g )(x) = g(f(x)) instead. This is common when a postfix notation is used, especially if functions are represented by exponents, as, for instance, in the study of group actions. See Dixon, John D.; Mortimer, Brian (1996), Permutation groups, Springer, էջ 5, ISBN0-387-94599-7
