#
Multivariate Splines and the 4 Color Map Problem

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Notes

We can always add edges to a subtriangulation, and obtain a
triangulation without adding vertices. The purpose of this
process is to be able to utilize unavoidable sets defined for
triangulations. Then the intersection of an unavoidable
configuration of the extended triangulation with the present
subtriangulation is an unavoidable configuration of the
subtriangulation. It is not empty because every vertex of the
triangulation is also a vertex of the subtriangulation.

[21-Apr-1997]