“…Accordingly, modifications in classical continuum theory have been made to incorporate small-scale/nonlocal effects. As a result of this, various nonlocal continuum theories such as couple stress theory (CST) [8], strain gradient theory (SGT) [9], Eringen's nonlocal theory (ENT) [10][11][12][13], nonlocal strain gradient theory (NSGT) [14,15] and surface elasticity theory [16,17] have been proposed. Using these theories, a vast literature dealing with the mechanical behavior of FG nanostructures is available, and Ghayesh and Farajpour [18] have presented a critical review of work up to 2019 [18].…”