Cai , MingchaoJu , Guoliang and Li , Jingzhi. (2024). Schur Complement Based Preconditioners for Twofold and Block Tridiagonal Saddle Point Problems.
            <i>Communications in Mathematical Research </i>. <i>40</i> (2).
            214-244.
         doi:10.4208/cmr.2023-0051