Lijie Mei, Changying Liu & Xinyuan Wu. (2020). An Essential Extension of the Finite-Energy Condition for Extended Runge-Kutta-Nyström Integrators when Applied to Nonlinear Wave Equations.
            <i>Communications in Computational Physics</i>. <i>22</i> (3).
            742-764.
         doi:10.4208/cicp.OA-2016-0141