@article{EJDE_2004__2004__a199,
     author = {Liu,  Yansheng},
     title = {Multiple positive solutions to fourth-order singular boundary-value problems in abstract spaces},
     journal = {Electronic journal of differential equations},
     year = {2004},
     volume = {2004},
     zbl = {1076.34068},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2004__2004__a199/}
}