1.
POKUTNYI, Oleksandr. Weakly nonlinear hyperbolic differential equation of the second order in Hilbert space. Topological Methods in Nonlinear Analysis. Online. 15 September 2024. Vol. 64, no. 1, pp. 279 - 294. [Accessed 23 February 2026]. DOI 10.12775/TMNA.2023.056.