MEDERSKI, Jarosław. Solutions to a nonlinear Schrödinger equation with periodic potential and zero on the boundary of the spectrum. Topological Methods in Nonlinear Analysis. Online. 1 December 2015. Vol. 46, no. 2, pp. 755 - 772. [Accessed 22 July 2024]. DOI 10.12775/TMNA.2015.067.