@article{01139217, title = {The symmetry of intersection numbers in group theory.}, journal = {Geometry \& Topology}, volume = {2}, year = {1998}, pages = {11-29}, doi = {10.2140/gt.1998.2.11}, zbl = {0897.20029}, language = {en}, url = {http://dml.mathdoc.fr/item/01139217} }
Scott, Peter. The symmetry of intersection numbers in group theory.. Geometry & Topology, Tome 2 (1998) pp. 11-29. doi : 10.2140/gt.1998.2.11. http://gdmltest.u-ga.fr/item/01139217/