@article{EJDE_2007__2007__a123,
     author = {Graef,  John R. and Henderson,  Johnny and Yang,  Bo},
     title = {Positive solutions of a nonlinear higher order boundary-value problem},
     journal = {Electronic journal of differential equations},
     year = {2007},
     volume = {2007},
     zbl = {1117.34023},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2007__2007__a123/}
}