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