@article{CMFD_2015_58_a3,
     author = {V. G. Zvyagin and S. V. Kornev},
     title = {Method of guiding functions for existence problems for periodic solutions of differential equations},
     journal = {Contemporary Mathematics. Fundamental Directions},
     pages = {59--81},
     publisher = {mathdoc},
     volume = {58},
     year = {2015},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/CMFD_2015_58_a3/}
}