We say that a random vector X = (X 1 , . . . , Xn) in R n is an n-dimensional version of a random variable Y if, for any a ∈ R n , the random variables a i X i and γ(a)Y are identically distributed, where γ : R n → [0, ∞) is called the standard of X. An old problem is to characterize those functions γ that can appear as the standard of an n-dimensional version. In this paper, we prove the conjecture of Lisitsky that every standard must be the norm of a space that embeds in L 0 . This result is almost optimal, as the norm of any finite-dimensional subspace of Lp with p ∈ (0, 2] is the standard of an n-dimensional version (p-stable random vector) by the classical result of P. Lèvy. An equivalent formulation is that if a function of the form f ( · K ) is positive definite on R n , where K is an origin symmetric star body in R n and f : R → R is an even continuous function, then either the space (R n , · K ) embeds in L 0 or f is a constant function. Combined with known facts about embedding in L 0 , this result leads to several generalizations of the solution of Schoenberg's problem on positive definite functions.