@article{GDZPPN001261541, title = {Inverse monoids and rational Schreier subsets of the free group.}, journal = {Semigroup forum}, volume = {44}, year = {1992}, pages = {137-148}, zbl = {0757.20017}, url = {http://dml.mathdoc.fr/item/GDZPPN001261541} }
Margolis, S.; Meakin, C.J. Inverse monoids and rational Schreier subsets of the free group.. Semigroup forum, Tome 44 (1992) pp. 137-148. http://gdmltest.u-ga.fr/item/GDZPPN001261541/