Reduction of Hamiltonian Systems, Affine Lie Algebras and Lax Equations. A.G. Reymann; M. Semenov-Tian-Shansky — 1979 Inventiones mathematicae
Reduction of Hamiltonian Systems, Affine Lie Algebras and Lax Equations II. M. Semenov-Tian-Shansky; A.G. Reyman — 1981 Inventiones mathematicae