Forced vibration analyses of FGP shallow shells with variable curvature J. Lu, C. Chiu, X. Zhang, S. Li, Z. Meng and W. Xu Eur. Phys. J. Plus, 136 10 (2021) 1016 Published online: 10 October 2021 DOI: 10.1140/epjp/s13360-021-02008-4