Superfluidity and collective oscillations of trapped Bose-Einstein condensates in a periodical potential C. Trallero-Giner, V. López-Richard, Y. Núñez-Fernández, M. Oliva, G.E. Marques and M.C. Chung Eur. Phys. J. D, 66 7 (2012) 177 Published online: 10 July 2012 DOI: 10.1140/epjd/e2012-30179-0