MikhailetsV. A. and MolybogaV. M. (2007) “Singularly perturbed periodic and semiperiodic differential operators”, Ukrains’kyi Matematychnyi Zhurnal, 59(6), pp. 785–797. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3345 (Accessed: 22November2024).