@article{01702853, title = {The co-rank conjecture for 3-manifold groups.}, journal = {Geometry \& Topology}, volume = {6}, year = {2002}, pages = {37-50}, doi = {10.2140/agt.2002.2.37}, zbl = {0983.57001}, language = {en}, url = {http://dml.mathdoc.fr/item/01702853} }
Leininger, Christopher J.; Reid, Alan W. The co-rank conjecture for 3-manifold groups.. Geometry & Topology, Tome 6 (2002) pp. 37-50. doi : 10.2140/agt.2002.2.37. http://gdmltest.u-ga.fr/item/01702853/