Mechanical instabilities of bubble clusters between parallel walls M. A. Fortes, M. E. Rosa, M. F. Vaz and P. I. C. Teixeira Eur. Phys. J. E, 15 4 (2004) 395-406 Published online: 30 November 2004 DOI: 10.1140/epje/i2004-10055-7