@article{SM_1994_78_2_a12,
     author = {L. M. Lerman and Ya. L. Umanskii},
     title = {Classification of four-dimensional integrable {Hamiltonian} systems and {Poisson} actions of},
     journal = {Sbornik. Mathematics},
     pages = {479--506},
     year = {1994},
     volume = {78},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1994_78_2_a12/}
}