@article{MAN_1980__252_163443,
     author = {John J. O'Sullivan and Jost-Hinrich Eschenburg},
     title = {Jacobi {Tensors} and {Ricci} {Curvature.}},
     journal = {Mathematische Annalen},
     pages = {1--26},
     publisher = {mathdoc},
     volume = {252},
     year = {1980},
     zbl = {0423.53035},
     url = {http://geodesic.mathdoc.fr/item/MAN_1980__252_163443/}
}