  This is a supplement for "Pearls in graph theory" -- a textbook written by
Nora Hartsfield and Gerhard Ringel.
  We discuss the following topics: Ramsey theory, Probabilistic method,
Deletion-contraction formulas, Matrix theorem, Graph-polynomials, Generating
functions, Minimum spanning trees, Marriage theorem and its relatives, Toroidal
graphs, Rado graph, Rewriting systems.
