@article{GDZPPN002441934, title = {Crossed squares and combinatorical homotopy.}, journal = {Mathematische Zeitschrift}, volume = {212}, year = {1993}, pages = {93-110}, zbl = {0789.55008}, url = {http://dml.mathdoc.fr/item/GDZPPN002441934} }
Ellis, Graham. Crossed squares and combinatorical homotopy.. Mathematische Zeitschrift, Tome 212 (1993) pp. 93-110. http://gdmltest.u-ga.fr/item/GDZPPN002441934/