@article{GDZPPN002432013, title = {Products of Conjugacy Classes in a Free Group: a Counterexample.}, journal = {Mathematische Zeitschrift}, volume = {192}, year = {1986}, pages = {167-182}, zbl = {0601.20034}, url = {http://dml.mathdoc.fr/item/GDZPPN002432013} }
Gersten, S.M. Products of Conjugacy Classes in a Free Group: a Counterexample.. Mathematische Zeitschrift, Tome 192 (1986) pp. 167-182. http://gdmltest.u-ga.fr/item/GDZPPN002432013/