@article{MS2_1975__37_166443,
     author = {Helmut Kaul and Stefan Hildebrandt and Kjell-Ove Widman},
     title = {Harmonic mappings into {Riemannian} manifolds with non-positive sectional curvature.},
     journal = {Mathematica Scandinavica},
     pages = {257--263},
     publisher = {mathdoc},
     volume = {37},
     year = {1975},
     zbl = {0321.53036},
     url = {http://geodesic.mathdoc.fr/item/MS2_1975__37_166443/}
}