Baoqing Liu and Qikui Du. (2013). The Coupling of NBEM and FEM for Quasilinear Problems in a Bounded or Unbounded Domain with a Concave Angle.
            <i>Journal of Computational Mathematics</i>. <i>31</i> (3).
            308-325.
         doi:10.4208/jcm.1212-m3906