Exact solutions of a nonpolynomial oscillator related to isotonic oscillator Qian Dong, Guo-Hua Sun, N. Saad and Shi-Hai Dong Eur. Phys. J. Plus, 134 11 (2019) 562 Published online: 12 November 2019 DOI: 10.1140/epjp/i2019-12980-7