 the Radon–Nikodym theorem follows as a special case of the Freudenthal spectral theorem.Riesz spaces have also seen application in mathematical economics through the work of Greek-American economist and mathematician Charalambos D. Aliprantis.If "X" is an ordered vector space and if "S" is a subset of "X" then an element "b" ∈ "X" is an upper bound (resp.