%0 Journal Article
%A Cao, Xifang
%A Kong, Qingkai
%A Wu, Hongyou
%A Zettl, Anton
%T Sturm-Liouville Problems Whose Leading Coefficient Function Changes Sign
%J Canadian journal of mathematics
%D 2003
%P 724-749
%V 55
%N 4
%U http://geodesic.mathdoc.fr/articles/10.4153/CJM-2003-031-0/
%R 10.4153/CJM-2003-031-0
%F 10_4153_CJM_2003_031_0