@InCollection{Borowiecki:1989,
  author    = "M. Borowiecki and D. Michalak",
  title     = "On hallian digraphs and their binding number",
  pages     = "33--37",
  year      = "1989",
  booktitle = "Combinatorics and graph theory, ISBN: 8301093005",
  publisher = "Polish Scientific Publishers",
  address   = "Warszawa",
  series    = "Banach Center Publications : Vol. 25",
}