@article{TMF_1993_95_1_a2,
     author = {L. V. Ryzhik and E. I. Shulman},
     title = {Symmetry algebra of nonlinear integrable equations},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {34--41},
     publisher = {mathdoc},
     volume = {95},
     number = {1},
     year = {1993},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1993_95_1_a2/}
}