@article{PFMT_2016_3_a6,
     author = {E. V. Musafirov},
     title = {Admissible perturbations of {Langford} system},
     journal = {Problemy fiziki, matematiki i tehniki},
     pages = {47--51},
     publisher = {mathdoc},
     number = {3},
     year = {2016},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/PFMT_2016_3_a6/}
}