1. P. Lax, Periodic solutions of the KdV equation, American Math. Soc., Lectures in App. Math. 5 (1974), 85–96.
2. S. Novikov, A periodic problem for the Korteweg-de Vries equation, Funct. Anal. 8 (1974), 54–66.
3. H. McKean, Integrable systems and algebraic curves, Lecture Notes in Mathematics (1979), Springer.
4. H. Flaschka and D. McLaughlin, Canonically conjugate variables for the Korteweg- de Vries equation and the Toda lattice with periodic boundary conditions, Prog. Theor. Phys. 55 2 (1976), 438–456.
5. S. Novikov, B. Dubrovin and V. Matveev, Nonlinear equations of Korteweg-de Vries type, finite-zone linear operators and Abelian manifolds, Uspekhi Mat. Nauk, Moscow 31 (1976), 55–136.