“…Various numerical discretization methods for FDE problems (e.g., finite differences, finite volumes, finite elements, spectral methods) can be found in the literature. We refer the reader to [14,19,21,24,26,37,39,40] and references therein. In the case of regular spatial domain subdivisions, the discretization matrices inherit a Toeplitz-like structure from the space-invariant property of the underlying operators that can be exploited for the design of ad hoc iterative schemes of multigrid and preconditioned Krylov type (see, e.g., [12,13,20,27,29,30]).…”