“…Several models were proposed to overcome difficulties related to the adoption of classical local models, generally due to the inability of retaining memory of the internal-length scale [20,21]. This was done by introducing non-simple explicit or implicit non-local models [22,23,13,24], which allow one to avoid ill-posed field-equations and mesh dependence in the numerical solutions. Within this framework, various approaches have been presented concerning higher-order models or second gradient models (Mindlin-Toupin type) [25,26,27,28,29,30,31], or also micromorphic continua [23], and in particular, micropolar continua [32], which can be considered non-local models of implicit type [33,34,14,35,36,37,38,39,40,41].…”