Jun Hu & Shangyou Zhang. (2020). An Error Analysis Method SPP-BEAM and a Construction Guideline of Nonconforming Finite Elements for Fourth Order Elliptic Problems.
            <i>Journal of Computational Mathematics</i>. <i>38</i> (1).
            195-222.
         doi:10.4208/jcm.1811-m2018-0162