“…Moreover, Hezari et al [30] presented a preconditioned variant of the GSOR (PGSOR) iterative method, Chen and Ma [21] established the AOR-Uzawa iterative method. For more iterative methods and Krylov subspace methods in real arithmetic for solving non-singular linear system (1.4), see [10,15,16,31,34] and references therein. When W, T are both symmetric positive semi-definite satisfying null(W ) ∩ null(T ) = {0}, then the coefficient matrix A of (1.1) is singular.…”