Integration of real-valued set functions in abstract Spaces
Peter D. Finch · Journal of the Australian Mathematical Society · 1964
Let an abstract space of points x and let ℳ be a σ-field of subsets of , that is a class of subsets of such that (i) ∈ ℳ, (ii) if M ∈ ℳ then — M ∈ ℳ and (iii) if {Mj} is any sequence of elements of ℳ then UjMj ∈ ℳ.