@article{MZ_1982__181_173235,
     author = {Sadao Sato},
     title = {Barta's {Inequalities} and the {First} {Eigenvalue} of a {Cap} {Domain} of a {2-Sphere.}},
     journal = {Mathematische Zeitschrift},
     pages = {313--318},
     publisher = {mathdoc},
     volume = {181},
     year = {1982},
     zbl = {0498.53034},
     url = {http://geodesic.mathdoc.fr/item/MZ_1982__181_173235/}
}