Lavrent’evA. S. (1999) “A singularly perturbed spectral problem for a biharmonic operator with Neumann conditions”, Ukrains’kyi Matematychnyi Zhurnal, 51(11), pp. 1467–1475. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4748 (Accessed: 24November2024).