Damped and sub-damped Lyman-α absorbers in z > 4 QSOs R. Guimarães, P. Petitjean, R. R. de Carvalho, S. G. Djorgovski, P. Noterdaeme, S. Castro, P. C. da R. Poppe and A. Aghaee A&A, 508 1 (2009) 133-140 Published online: 15 October 2009 DOI: 10.1051/0004-6361/200811541