Simple model for reverse buoyancy in a vibrated granular systemG. Gutiérrez, O. Pozo, L. I. Reyes, R. Paredes V., J. F. Drake and E. OttEurophys. Lett., 67 3 (2004) 369-375DOI: https://doi.org/10.1209/epl/i2003-10300-3