“…In some cases, this method facilitates a more straightforward, and operator theory flavored, analysis of periodic homogenization problems. In recent years periodic unfolding has been applied to a large variety of multiscale problems; e.g., see [11,17,37,38,34,43,10,29,42,21]. For a systematic investigation of two-scale calculus associated with the use of the periodic unfolding method we refer to [14,44,45,37,12].…”