Superfluidity and collective oscillations of trapped Bose-Einstein condensates in a periodical potentialC. Trallero-Giner, V. López-Richard, Y. Núñez-Fernández, M. Oliva, G.E. Marques and M.C. ChungEur. Phys. J. D, 66 7 (2012) 177DOI: https://doi.org/10.1140/epjd/e2012-30179-0