Effect of an electric field on the bifurcation of a biaxially stretched incompressible slab rubber R. Díaz-Calleja, M. J. Sanchis and E. Riande Eur. Phys. J. E, 30 4 (2009) 417-426 Published online: 15 December 2009 DOI: 10.1140/epje/i2009-10541-4