Upgrading from:

Algebra`SymmetricPolynomials`

New functions SymmetricPolynomial and SymmetricReduction have been added to the built-in Mathematica kernel.

The degree of the polynomial is now given as the first argument for SymmetricPolynomial:

Version 5.2 << Algebra`SymmetricPolynomials`; SymmetricPolynomial[{x, y, z, t}, 3]

SymmetricReduction is now a built-in function:

Version 5.2 SymmetricReduction[(x + y)^2 + (x + z)^2 + (z + y)^2, {x, y, z}]