“…In the second-half of the last century, the development of systems and control theory, together with the achievements of digital control and signal processing, has set the stage for renewed interest in the study of periodic systems, both in continuous and discrete time; see, e.g., [29,54,44,12,52,14] and the survey papers [3,4]. This has been amplified by specific application demands in the aerospace realm [21,30,20], computer control of industrial processes [5] and communication systems [43,12,42,53].…”