@article{RM_1961_16_4_a16,
     author = {M. M. Khapaev},
     title = {Linear differential equations with small coefficients of several higher derivatives in the neighborhood of regular singular points of the equation},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {16},
     number = {4},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1961_16_4_a16/}
}