@article{CMH_1976__51_139656,
     author = {Michael N. Dyer},
     title = {Projective k-invariants},
     journal = {Commentarii mathematici Helvetici},
     pages = {259--278},
     publisher = {mathdoc},
     volume = {51},
     year = {1976},
     zbl = {0329.55009},
     url = {http://geodesic.mathdoc.fr/item/CMH_1976__51_139656/}
}