Pseudorapidity distributions of charged particles as a function of centrality in Pb-Pb collisions at 158 and 40GeV per nucleon incident energy NA50Collaboration, M.C. Abreu, B. Alessandro, C. Alexa, R. Arnaldi, M. Atayan, C. Baglin, A. Baldit, M. Bedjidian, S. Beole, V. Boldea, P. Bordalo, G. Borges, A. Bussiere, L. Capelli, C. Castanier,