@article{MOMA_1984__97_178173,
     author = {H.G. Kaper and M.K. Kwong and A. Zettl},
     title = {Singular {Sturm-Liouville} {Problems} with {Nonnegative} and {Indefinite} {Weights.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {177--190},
     publisher = {mathdoc},
     volume = {97},
     year = {1984},
     zbl = {0535.34019},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1984__97_178173/}
}