@article{PORMA_1965__24_3_114958,
     author = {van Vleck, F.S.},
     title = {A bifurcation theorem for a class of differential equations},
     journal = {Portugaliae mathematica},
     pages = {125--130},
     publisher = {mathdoc},
     volume = {24},
     number = {3},
     year = {1965},
     mrnumber = {0222369},
     zbl = {0161.28901},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1965__24_3_114958/}
}