1. G. Darboux, Leçons sur le systèmes orthogonaux et les coordonnées curvilignes, Paris, 1910.
2. B. A. Dubrovin and S. P. Novikov, “The Hamiltonian formalism of one-dimensional systems of hydrodynamic type and the Bogolyubov-Whitham averaging method,” Dokl. Akad. Nauk SSSR,27, 665–654 (1983).
3. B. A. Dubrovin and S. P. Novikov, “Hydrodynamics of weakly deformed soliton lattices: Differential geometry and Hamiltonian theory,” Usp. Mat. Nauk,44, 35–124 (1989).
4. S. P. Tsarev, “The geometry of Hamiltonian systems of hydrodynamic type. Generalized hodograph method,” Izv. Akad. Nauk SSSR, Ser. Mat.,54, No. 5, 1048–1068 (1990).
5. B. Dubrovin, “Integrable systems in topological field theory,” Nuclear Phys. B,379, 627–689 (1992).