Riemann Surfaces
  General domains of analytic functions of one complex variable. Surfaces are
  locally described by holomorphic functions.
  For example, a model of a concrete Riemann surface may be given as a
  triangular or rectangular mesh of a branched covering of a planar domain.
References
  
    - L.V. Ahlfors, L. Sario: Riemann Surfaces, Princeton University Press (1960).
 
    - Otto Forster: Riemannsche Flächen, Springer (1997).
 
    - Hermann Weyl: Die Idee der Riemannschen Fläche, Teubner (1955).
 
  
Technical
Note
  As a guide, meshes should have no holes, no degenerate triangles and
  elements, no duplicate vertices. Surfaces should have meshes with an adjacency
  relation.