If R is a right non-singular ring
(with 1) and Q is its (R. E. Johnson) maximal right quotient ring, then the
R-epimorphism ∑ipi⊗ qi→∑piqi from (Q ⊗RQ)R to QR is not in general a
monomorphism; in this paper we show that it is if, and only if, for each
q ∈ Q,(R : q) = {r ∈ R|qr ∈ R} contains a finitely generated large right ideal of R.
As a corollary to this we obtain: a (Von Neumann) regular ring R is right
selfinjective if and only if every finitely generated nonsingular right R-module is
projective.