@article{PMIHES_1987__65__35_0,
     author = {Burns, Keith and Spatzier, Ralf},
     title = {Manifolds of nonpositive curvature and their buildings},
     journal = {Publications Math\'ematiques de l'IH\'ES},
     pages = {35--59},
     publisher = {Institut des Hautes \'Etudes Scientifiques},
     volume = {65},
     year = {1987},
     mrnumber = {908215},
     zbl = {0643.53037},
     language = {en},
     url = {http://www.numdam.org/item/PMIHES_1987__65__35_0/}
}