Large- N Weinberg-Tomozawa interaction and spin-flavor symmetry C. Garcıa-Recio, J. Nieves and L. L. Salcedo Eur. Phys. J. A, 31 4 (2007) 491-494 Published online: 20 March 2007 DOI: 10.1140/epja/i2006-10273-7