I. Yamazaki, X. S. Li & E. G. Ng. (2020). Preconditioning Schur Complement Systems of Highly-Indefinite Linear Systems for a Parallel Hybrid Solver.
            <i>Numerical Mathematics: Theory, Methods and Applications</i>. <i>3</i> (3).
            352-366.
         doi:10.4208/nmtma.2010.33.5