A. H. H. Encinas, J. Martín-Vaquero, A. Queiruga-Dios, and V. Gayoso-Martínez, “Efficient high-order finite difference methods for nonlinear Klein–Gordon equations. I: Variants of the phi-four model and the form-I of the nonlinear Klein–Gordon equation”, NAMC, vol. 20, no. 2, pp. 274–290, Apr. 2015, doi: 10.15388/NA.2015.2.9.