PEJSACHOWICZ, Jacobo. Bifurcation of solutions of $U(1)$-equivariant semilinear boundary value problems. Topological Methods in Nonlinear Analysis. Online. 26 February 2023. Vol. 61, no. 1, pp. 491 - 500. [Accessed 17 May 2025]. DOI 10.12775/TMNA.2022.056.