Dobkevich, Maria, and Felix Sadyrbaev. “Types and Multiplicity of Solutions to Sturm–Liouville Boundary Value Problem”. Mathematical Modelling and Analysis 20, no. 1 (February 3, 2015): 1-8. Accessed April 28, 2024. https://journals.vilniustech.lt/index.php/MMA/article/view/981.