Title:  Hamiltonian systems of negative curvature are hyperbolic 
 Authors:  A.A. Agrachev, N.N. Chtcherbakova 
 Journal title:  Russian Math. Dokl. 
 Year:  2005 
 Volume:  400 
 Pages:  295-298 
 Abstract:  
The curvature and the reduced curvature are basic differential invariants of the pair: 
 File:  
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