@article{TMF_1982_51_1_a1,
     author = {A. N. Leznov and V. G. Smirnov and A. B. Shabat},
     title = {The~group of internal symmetries and the conditions of integrability of two-dimensional dynamical systems},
     journal = {Teoreti\v{c}eska\^a i matemati\v{c}eska\^a fizika},
     pages = {10--21},
     publisher = {mathdoc},
     volume = {51},
     number = {1},
     year = {1982},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TMF_1982_51_1_a1/}
}