“…In general, different nonlocal theoretical frameworks can be developed. Examples of nonlocal approaches that should be mentioned for completeness purposes are the strain and stress gradient theories [ 58 , 59 , 60 ], the modified couple stress theory [ 61 , 62 , 63 , 64 ], and the ones based on micropolar formulations [ 65 , 66 , 67 ]. A comprehensive literature review concerning nonlocal elasticity can be found in the paper by Zhao et al [ 68 ] for completeness purposes.…”