@article{AA_1991_3_1_a1,
     author = {M. V. Babich},
     title = {Smoothness of real finite-gap solutions of equations connected with the {sine-Gordon} equation},
     journal = {Algebra i analiz},
     pages = {57--66},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AA_1991_3_1_a1/}
}