1. A. B. Shabat and R. I. Yamilov, ?Exponential systems of type I and Cartan matrices [in Russian],? Preprint, Bashkir Branch, Acad. Sci. USSR, Ufa (1981).
2. M. A. Olshanetsky and A. M. Perelomov, Phys. Rep., 71, 313?400 (1981).
3. A. N. Leznov and M. V. Saveliev, Group Methods of Integration of Nonlinear Dynamical Systems [in Russian], Nauka, Moscow (1985); English transl.: Group-Theoretical Methods for Integration of Nonlinear Dynamical Systems, Birkhäuser, Basel (1992).
4. S. P. Tsarev, Theor. Math. Phys., 122, 121?133 (2000).
5. G. Darboux, Lecons sur la théorie générale des surfaces et les applications gé ométriques du calcul infinitésimal, Vol. 2, Gautier-Villars, Paris (1915).