@article{DAN_1971_199_6_a5,
     author = {Yu. S. Kolesov and V. F. Chaplygin},
     title = {On nonoscillation of solutions to singularly disturbed equations of second order},
     journal = {Doklady Akademii Nauk},
     pages = {1240--1242},
     publisher = {mathdoc},
     volume = {199},
     number = {6},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_199_6_a5/}
}