@article{GDZPPN00206233X,
title = {G Maps and the Projective Class Group},
journal = {Commentarii mathematici Helvetici},
volume = {51},
year = {1976},
pages = {611-626},
zbl = {0365.55005},
url = {http://dml.mathdoc.fr/item/GDZPPN00206233X}
}
Petrie, Ted. G Maps and the Projective Class Group. Commentarii mathematici Helvetici, Tome 51 (1976) pp. 611-626. http://gdmltest.u-ga.fr/item/GDZPPN00206233X/