@article{MZ_1990__203_3_174117,
     author = {Viktor Schroeder and Susana Fornari},
     title = {Ramified {Coverings} with {Nonpositive} {Curvature.}},
     journal = {Mathematische Zeitschrift},
     pages = {123--128},
     publisher = {mathdoc},
     volume = {203},
     number = {3},
     year = {1990},
     zbl = {0694.53040},
     url = {http://geodesic.mathdoc.fr/item/MZ_1990__203_3_174117/}
}