@article{01925941,
title = {Crossed complexes, and free crossed resolutions for amalgamated sums and HNN-extensions of groups.},
journal = {Georgian Mathematical Journal},
volume = {9},
year = {2002},
pages = {623-644},
zbl = {1030.55013},
language = {en},
url = {http://dml.mathdoc.fr/item/01925941}
}
Brown, R.; Moore, E.J.; Porter, T.; Wensley, C.D. Crossed complexes, and free crossed resolutions for amalgamated sums and HNN-extensions of groups.. Georgian Mathematical Journal, Tome 9 (2002) pp. 623-644. http://gdmltest.u-ga.fr/item/01925941/