@article{TMF_1987_72_3_a0,
     author = {V. A. Arkad'ev and A. K. Pogrebkov and M. K. Polivanov},
     title = {Expansions with respect to squares, symplectic and poisson structures associated with the {Sturm--Liouville} {problem.~I}},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {323--339},
     publisher = {mathdoc},
     volume = {72},
     number = {3},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1987_72_3_a0/}
}