FĂRCĂȘEANU, M., GRECU, A., MIHĂILESCU, M., & STANCU-DUMITRU, D. (2021). Perturbed eigenvalue problems: an overview. Studia Universitatis Babeș-Bolyai Mathematica, 66(1), 55–73. https://doi.org/10.24193/subbmath.2021.1.05