@article{MZ_1987__195_183699,
     author = {Y.Y. Baldin and Maria H. Noronha},
     title = {Some {Complete} {Manifolds} with {Non-Negative} {Curvature} {Operator.}},
     journal = {Mathematische Zeitschrift},
     pages = {383--390},
     publisher = {mathdoc},
     volume = {195},
     year = {1987},
     zbl = {0602.53033},
     url = {http://geodesic.mathdoc.fr/item/MZ_1987__195_183699/}
}