Yangian algebra in the bi-qubit system and mixed light pseudoscalar meson state Li-Guo Qin, Li-Jun Tian and Guo-Hong Yang Eur. Phys. J. C, 72 3 (2012) 1934 Published online: 27 March 2012 DOI: 10.1140/epjc/s10052-012-1934-0