An error bound for the USAOR method

Suppose Ax = b is a system of linear equations where the matrix A is symmetric positive definite and consistently ordered. A bound for the norm of the error ɛ k = x - x k of the USAOR method in terms of the norms of δ k = x k - x k - 1 and δ k + 1 = x k + 1 - x k and their inner product are derived.