“…Without question, the study of periodic systems in general and Floquet theory in particular has been central to the differential equations theorist for some time. Researchers have explored these topics for ordinary differential equations [8,14,15,22,28,29,34,36], partial differential equations [7,9,15,25], differential-algebraic equations [13,26], and discrete dynamical systems [3,23,35]. Certainly [27] is a landmark paper in the area.…”