@article{MZM_1991_50_4_a0,
     author = {T. Ya. Azizov and V. L. Khatskevich},
     title = {Some applications of the theory of operators in {Krein} spaces to the solvability of nonlinear {Hamiltonian} systems},
     journal = {Matemati\v{c}eskie zametki},
     pages = {3--9},
     publisher = {mathdoc},
     volume = {50},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1991_50_4_a0/}
}