“…Weyl functions (also called Weyl-Titchmarsh or M-functions) and their generalizations are an important and much used tool in the spectral theory of differential equations (see a necessarily small part of recent papers and books on this topic and various references therein [3-5, 10, 11, 14, 16-18, 20, 32, 37, 41, 49, 51]). Following the seminal work [27] and more general constructions in [45,49] (see also some references therein), one can use structured operators to solve inverse problems for Krein, Dirac, canonical, nonclassical and non-self-adjoint systems and their discrete analogues (see, for instance, [2,15,16,37,[40][41][42]). It was proved in [16,36,37,[40][41][42] that the kernels of these structured operators are connected with the Weyl functions via some kinds of Fourier transformations and can be recovered directly from the Weyl functions.…”