The Araucaria Project: VLT-spectroscopy of blue massive stars in NGC 55 N. Castro, A. Herrero, M. Garcia, C. Trundle, F. Bresolin, W. Gieren, G. Pietrzyński, R.-P. Kudritzki and R. Demarco A&A, 485 1 (2008) 41-50 Published online: 28 April 2008 DOI: 10.1051/0004-6361:200809399