Helicity amplitudes and electromagnetic decays of hyperon resonances T. Van Cauteren, J. Ryckebusch, B. Metsch and H. -R. Petry Eur. Phys. J. A, 26 3 (2005) 339-359 Published online: 26 January 2006 DOI: 10.1140/epja/i2005-10190-3