%0 Journal Article
%A L. A. Lepin
%T The method of lower and upper functions for second-order differential equations with singularities
%J Differencialʹnye uravneniâ
%D 1987
%P 1632-1634
%V 23
%N 9
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1987_23_9_a22/
%G ru
%F DE_1987_23_9_a22