Liu , Kai and Wu , Xinyuan. (2015). High-Order Symplectic and Symmetric Composition Methods for Multi-Frequency and Multi-Dimensional Oscillatory Hamiltonian Systems.
            <i>Journal of Computational Mathematics</i>. <i>33</i> (4).
            356-378.
         doi:10.4208/jcm.1502-m2014-0082