%0 Journal Article %A Ahlbrandt, Calvin D. %A Hinton, Don B. %A Lewis, Roger T. %T Necessary and Sufficient Conditions for the Discreteness of the Spectrum of Certain Singular Differential Operators %J Canadian journal of mathematics %D 1981 %P 229-246 %V 33 %N 1 %U http://geodesic.mathdoc.fr/articles/10.4153/CJM-1981-019-1/ %R 10.4153/CJM-1981-019-1 %F 10_4153_CJM_1981_019_1