@article{02104400, title = {Foldable cubical complexes of nonpositive curvature.}, journal = {Geometry \& Topology}, volume = {8}, year = {2004}, pages = {603-622}, doi = {10.2140/agt.2004.4.603}, zbl = {1055.20035}, language = {en}, url = {http://dml.mathdoc.fr/item/02104400} }
Xie, Xiangdong. Foldable cubical complexes of nonpositive curvature.. Geometry & Topology, Tome 8 (2004) pp. 603-622. doi : 10.2140/agt.2004.4.603. http://gdmltest.u-ga.fr/item/02104400/