@article{UZMU_1956_181_181_a2,
     author = {I. M. Sobol'},
     title = {Positive solutions of linear differential equations with retardation},
     journal = {Uchenye Zapiski Moskovskogo Gosudarstvennogo Universiteta},
     pages = {45--56},
     publisher = {mathdoc},
     volume = {181},
     number = {181},
     year = {1956},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/UZMU_1956_181_181_a2/}
}