Johnen A., Remacle J.-F., Geuzaine C. Geometrical validity of curvilinear finite elements. J. Comput. Phys. 2013, 233:359-372.
Bergot M., Cohen G., Duruflé M. Higher-order finite elements for hybrid meshes using new nodal pyramidal elements. J. Sci. Comput. 2010, 42(3):345-381. 10.1007/s10915-009-9334-9.
Geuzaine C., Remacle J. Gmsh: a 3-D finite element mesh generator with built-in pre- and post-processing facilities. Int. J. Numer. Methods Eng. 2009, 79(11):1309-1331.