@article{MZ_1976__150_172402,
     author = {Herbert Amann},
     title = {Nonlinear {Eigenvalue} {Problems} {Having} {Precisely} {Two} {Solutions.}},
     journal = {Mathematische Zeitschrift},
     pages = {27--38},
     publisher = {mathdoc},
     volume = {150},
     year = {1976},
     zbl = {0329.35027},
     url = {http://geodesic.mathdoc.fr/item/MZ_1976__150_172402/}
}