Mikhailets, V.A., and V.M. Molyboga. “On Spectral Gaps of the Hill—Schrödinger Operator With Singular Potential”. Reports of the National Academy of Sciences of Ukraine, no. 10 (May 20, 2024): 3–8. Accessed July 28, 2025. https://nasu-periodicals.org.ua/index.php/dp/article/view/3019.