The model of Hénon and Heiles
The paper of Hénon and Heiles
The model
Poincaré sections
The paper of Gustavson.
Figure 1
,
Figure 2
Comparison with the level curves: 
E=1/100
,
E=1/12
,
E=1/8
,
E=1/6
The norms of the generating function