@article{IVM_1968_4_a5,
     author = {S. Karimov},
     title = {Periodic solutions of nonlinear systems of difference equations in two variables},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {33--39},
     year = {1968},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_1968_4_a5/}
}