Nguyen, T. T. H., D. T. Quyet, and T. H. A. Vu. “Liouville Type Theorems for Kirchhoff Sub-Elliptic Equations Involving $\Delta_\lambda$-Operators”. Topological Methods in Nonlinear Analysis, vol. 62, no. 1, Sept. 2023, pp. 327-40, doi:10.12775/TMNA.2022.071.