Exact solutions of the generalized two-photon and two-qubit Rabi models Jie Peng, Zhongzhou Ren, Guangjie Guo, Guoxing Ju and Xiaoyong Guo Eur. Phys. J. D, 67 8 (2013) 162 Published online: 01 August 2013 DOI: 10.1140/epjd/e2013-40183-5