@article{PORMA_2003__60_3_51141,
     author = {He, Xiaoming and Ge, Weigao},
     title = {Positive solutions for semipositone  boundary value problems.},
     journal = {Portugaliae mathematica},
     pages = {253--262},
     publisher = {mathdoc},
     volume = {60},
     number = {3},
     year = {2003},
     zbl = {1055.34032},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_2003__60_3_51141/}
}