 For formula_340, a distribution of order "k" is a distribution of order ≤ "k" that is not a distribution of order ≤ "k - 1".A distribution is said to be of finite order if there is some integer "k" such that it is a distribution of order ≤ "k', and the set of distributions of finite order is denoted by formula_341.Note that if formula_342 then formula_343 so that formula_341 is a vector subspace of formula_46 and furthermore, formula_346 if and only if formula_347.