@article{DAN_1969_189_6_a0,
     author = {M. A. Belyaeva},
     title = {Approximate solution of a system of ordinary differential equations with small parameter multiplying the derivatives},
     journal = {Doklady Akademii Nauk},
     pages = {1167--1170},
     publisher = {mathdoc},
     volume = {189},
     number = {6},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1969_189_6_a0/}
}