@book{Skupień:1989,
  editor    = "Z. Skupień and M. Borowiecki",
  title     = "Combinatorics and graph theory, ISBN: 8301093005",
  publisher = "Polish Scientific Publishers",
  address   = "Warszawa",
  pages     = "251",
  year      = "1989",
  number    = "Vol. 25",
}