FARKAS, Csaba, KAJÁNTÓ, Sándor and VARGA, Csaba. Lower semicontinuity of Kirchhoff-type energy functionals and spectral gaps on (sub)Riemannian manifolds. Topological Methods in Nonlinear Analysis. Online. 16 July 2023. Vol. 61, no. 2, pp. 743 - 760. [Accessed 22 July 2024]. DOI 10.12775/TMNA.2022.034.