@article{IM2_1972_6_3_a10,
     author = {S. A. Lomov},
     title = {The method of perturbations for singular problems},
     journal = {Izvestiya. Mathematics },
     pages = {631--648},
     publisher = {mathdoc},
     volume = {6},
     number = {3},
     year = {1972},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1972_6_3_a10/}
}