R. SELVAMANI, R. LOGANATHAN, and F. EBRAHIMI, “Nonlocal State-Space Strain Gradient Approach to the Vibration of Piezoelectric Functionally Graded Nanobeam”, Eng. Trans., vol. 70, no. 4, pp. 319–338, Dec. 2022, doi: 10.24423/EngTrans.2242.20221020.