@article{10_1007_s10492_007_0006_5,
     author = {L\"u, Haishen and O'Regan, Donal and Agarwal, Ravi P.},
     title = {Existence to singular boundary value problems with sign changing nonlinearities using an approximation method approach},
     journal = {Applications of Mathematics},
     pages = {117--135},
     publisher = {mathdoc},
     volume = {52},
     number = {2},
     year = {2007},
     doi = {10.1007/s10492-007-0006-5},
     mrnumber = {2305869},
     zbl = {1164.34351},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1007/s10492-007-0006-5/}
}