@article{10_1007_s10587_012_0052_3,
     author = {Ma, Ruyun and Chen, Ruipeng},
     title = {Existence of one-signed solutions of nonlinear four-point boundary value problems},
     journal = {Czechoslovak Mathematical Journal},
     pages = {593--612},
     publisher = {mathdoc},
     volume = {62},
     number = {3},
     year = {2012},
     doi = {10.1007/s10587-012-0052-3},
     mrnumber = {2984621},
     zbl = {1265.34053},
     language = {en},
     url = {https://geodesic-test.mathdoc.fr/articles/10.1007/s10587-012-0052-3/}
}