@phdthesis{ Dohmen:1993:CPG,
  author = {Klaus Dohmen},
  title = {{Chromatische Polynome von Graphen und Hypergraphen}},
  year = {1993},
  month = {November},
  type = {{Dissertation (PhD Thesis)}},
  school = {Heinrich-Heine-Universität Düsseldorf},
  keywords = {graph, hypergraph, chromatic polynomial, broken
                  circuit, deletion-contraction, bounds}
}