@article{CMH_1994__69_4_140335,
     author = {Takashi Shioya},
     title = {Mass of rays in {Alexandrov} spaces of nonnegative curvature.},
     journal = {Commentarii mathematici Helvetici},
     pages = {208--228},
     year = {1994},
     volume = {69},
     number = {4},
     zbl = {0818.53080},
     url = {http://geodesic.mathdoc.fr/item/CMH_1994__69_4_140335/}
}