  We show that every real nonnegative polynomial $f$ can be approximated as
closely as desired by a sequence of polynomials $\{f_\epsilon\}$ that are sums
of squares. Each $f_\epsilon$ has a simple et explicit form in terms of $f$ and
$\epsilon$. A special representation is also obtained for convex polynomials,
nonnegative on a convex semi-algebraic set.
