1. V. E. Zakharov and L. D. Faddeev, "The Korteweg?de Vries equation is a completely integrable Hamiltonian system," Funkts. Anal.,5, No. 4, 18?27 (1971).
2. C. S. Gardner, "Korteweg?de Vries equation and generalizations, IV," J. Math. Phys.,12, No. 8, 1548?1551 (1971).
3. I. M. Gel'fand and L. A. Dikii, "Asymptotic resolvents of Sturm?Liouville equations and the algebra of Korteweg?de Vries equations," Usp. Mat. Nauk,30, No. 5, 67?100 (1975).
4. I. M. Gel'fand and L. A. Dikii, "Fractional powers of operators and Hamiltonian systems," Funkts. Anal.,10, No. 4, 13?29 (1976).
5. I. M. Gel'fand and L. A. Dikii, "Resolvents and Hamiltonian systems," Funkts. Anal.,11, No. 2, 11?27 (1977).