@article{PavlovicD:4c,
  title = "A categorical setting for the 4-Colour Theorem",
  author = "Dusko Pavlovic",
  year = "1995",
  journal = "J.~Pure Appl. Algebra",
  pages = "75--88",
  url = "ftp://ftp.kestrel.edu/pub/papers/pavlovic/4c.ps",
  volume = "102",
}