@article{02104399, title = {Commutators and squares in free groups.}, journal = {Geometry \& Topology}, volume = {8}, year = {2004}, pages = {595-602}, doi = {10.2140/agt.2004.4.595}, zbl = {1055.20025}, language = {en}, url = {http://dml.mathdoc.fr/item/02104399} }
Sarkar, Sucharit. Commutators and squares in free groups.. Geometry & Topology, Tome 8 (2004) pp. 595-602. doi : 10.2140/agt.2004.4.595. http://gdmltest.u-ga.fr/item/02104399/