@article{GDZPPN00206894X,
title = {The geometric invariants of direct products of virtually free groups.},
journal = {Commentarii mathematici Helvetici},
volume = {69},
year = {1994},
pages = {39-48},
zbl = {0834.20039},
url = {http://dml.mathdoc.fr/item/GDZPPN00206894X}
}
Meinert, Holger. The geometric invariants of direct products of virtually free groups.. Commentarii mathematici Helvetici, Tome 69 (1994) pp. 39-48. http://gdmltest.u-ga.fr/item/GDZPPN00206894X/