V. T. T. Anh, D. H. Bich and N. D. Duc, Nonlinear post-buckling of thin FGM annular spherical shells under mechanical loads and resting on elastic foundations, Vietnam J. Mech. 36 (2014) 291–306. DOI: https://doi.org/10.15625/0866-7136/36/4/4243.