@article{10_4153_CMB_1997_004_4,
     author = {Dongsheng, Zhao},
     title = {On projective {Z-frames}},
     journal = {Canadian mathematical bulletin},
     pages = {39--46},
     year = {1997},
     volume = {40},
     number = {1},
     doi = {10.4153/CMB-1997-004-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1997-004-4/}
}