@article{CMH_1984__59_139983,
     author = {T.Y. Lam and Z.D. Dai},
     title = {Levels in algebra and topology.},
     journal = {Commentarii mathematici Helvetici},
     pages = {376--424},
     publisher = {mathdoc},
     volume = {59},
     year = {1984},
     zbl = {0546.10017},
     url = {http://geodesic.mathdoc.fr/item/CMH_1984__59_139983/}
}