@article{MZ_1981__176_183632,
     author = {Emanuel, Jr. Sperner},
     title = {Spherical {Symmetrization} and {Eigenvalue} {Estimates.}},
     journal = {Mathematische Zeitschrift},
     pages = {75--86},
     publisher = {mathdoc},
     volume = {176},
     year = {1981},
     zbl = {0464.49009},
     url = {http://geodesic.mathdoc.fr/item/MZ_1981__176_183632/}
}