1. Benenti S (1992) Orthogonal separable dynamical systems. In: Proceedings of conference on differential geometry and its applications, Opava, Czechoslovakia, pp 163–184
2. Benenti S (2004) Separability on Riemannian manifolds. Unpublished. http://www2.dm.unito.it/~benenti/
3. Burghelea D, Kuiper NH (1969) Hilbert manifolds. Ann Math 90:379–417
4. Clément Ph, Heijmans HJAM (1987) One-parameter semigroups. CWI monographs, vol 5. North Holland, Amsterdam
5. Delaleau E, Respondek W (1995) Lowering the orders of derivatives of controls in generalized state space systems. J Math Syst Estim Control 5(3):375–378