Multistable and excitable behavior in semiconductor ring lasers with broken Z2-symmetryL. Gelens, S. Beri, G. Van der Sande, G. Verschaffelt and J. DanckaertEur. Phys. J. D, 58 2 (2010) 197-207DOI: https://doi.org/10.1140/epjd/e2010-00042-7