Distance determination to NGC 55 from the planetary nebula luminosity function G. C. Van de Steene, G. H. Jacoby, C. Praet, R. Ciardullo and H. Dejonghe A&A, 455 3 (2006) 891-896 Published online: 16 August 2006 DOI: 10.1051/0004-6361:20053475