Multistable and excitable behavior in semiconductor ring lasers with broken Z2-symmetry L. Gelens, S. Beri, G. Van der Sande, G. Verschaffelt and J. Danckaert Eur. Phys. J. D, 58 2 (2010) 197-207 Published online: 02 March 2010 DOI: 10.1140/epjd/e2010-00042-7