@article{FAA_1979_13_1_a1,
     author = {I. M. Gel'fand and L. A. Dikii},
     title = {Integrable nonlinear equations and the {Liouville} theorem},
     journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a},
     pages = {8--20},
     publisher = {mathdoc},
     volume = {13},
     number = {1},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FAA_1979_13_1_a1/}
}