@article{NUMA_1987__51_133187,
     author = {Wolf-J\"urgen Beyn},
     title = {On {Invariant} {Closed} {Curves} for {One-Step} {Methods.}},
     journal = {Numerische Mathematik},
     pages = {103--122},
     year = {1987},
     volume = {51},
     zbl = {0617.65082},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1987__51_133187/}
}