F. A. Haggar

Sufficient conditions for dynamical systems to have pre-symplectic or pre-implectic structures

G. R. W. Quispel, G. Quispel, F. Haggar, 1999 .

k-integrals and k-Lie symmetries in discrete dynamical systems

G. R. W. Quispel, G. Quispel, H. Capel, 1996 .