Two papers by UB researchers have been named among the ten most cited articles worldwide produced in Catalan universities, according to data provided by the National Citation Report in its study "Bibliometric Characterization of Scientific Production in Catalonia (1996-2006)". The first article, co-written by Pilar Ruiz-Lapuente, was "Measurements of Omega and Lambda from 42 high-redshift supernovae" and appeared in Astrophysical Journal in 1999. With 2,318 citations, it ranked second in scientific impact. Ruiz-Lapuente is an expert in the UB research group on Astronomy and Astrophysics. The second article, written by Julio Rozas, held eighth position in scientific impact with 950 citations. His paper was "DnaSP version: an integrated programme for molecular population genetics and molecular evolution analysis", published in Bioinformatics in 1999). Rozas is a member of the UB research group on Molecular Evolutionary Genetics.