@article{vandeSteene:2031,
      author        = "van de Steene, G. C. and  Jacoby, G. H. and  Praet, C. and
                        Ciardullo, R. and  Dejonghe, H.",
      title         = "{Distance determination to NGC 55 from the planetary
                       nebula luminosity function}",
      year          = "2006",
}