BENEVIERI, Pierluigi, CALAMAI, Alessandro, FURI, Massimo and PERA, Maria Patrizia. The Brouwer degree associated to classical eigenvalue problems and applications to nonlinear spectral theory. Topological Methods in Nonlinear Analysis. Online. 13 December 2021. Vol. 59, no. 2A, pp. 499 - 523. [Accessed 28 June 2025]. DOI 10.12775/TMNA.2021.006.