Generalizations of Borg's uniqueness theorem to the case of nonseparated boundary conditions

Inverse Sturm–Liouville problems and generalizations of Borg's uniqueness theorem to the case of general boundary conditions are considered. Chudov, Marchenko, Krein, Karaseva and authors' generalizations are adduced. New generalizations of Borg, Marchenko and Karaseva's uniqueness theorem to the case of nonseparated boundary conditions are obtained. Appropriate examples and counterexample are given.