1. V. A. Marchenko, Sturm–Liouville Operators and Their Applications (Naukova Dumka, Kiev, 1977) [in Russian].
2. B. M. Levitan, inverse Sturm–Liouville problems (Nauka, Moscow, 1984) [in Russian].
3. G. Freiling and V. A. Yurko, Inverse Sturm–Liouville Problems and Their Applications (NOVA Sci. Publ., New York, 2001).
4. V. A. Yurko, Method of Spectral Mappings in the Inverse Problem Theory (VSP, Utrecht, 2002).
5. V. A. Yurko, Introduction to the Theory of Inverse Spectral Problems (Fizmatlit, Moscow, 2007) [in Russian].