“…Among higher gradient elasticity models [26,27,3,24,20,25] one of the very first models considered in the literature is the so called indeterminate couple stress model [9,28,42,19] in which the higher gradient contributions only enter through gradients of the continuum rotation, i.e. the total elastic energy can be written as W (∇u, ∇(∇u)) = W lin (sym∇u) + W curv (∇curl u).…”