@article{GDZPPN002066076, title = {Abelian normal subgroups of two-knot groups.}, journal = {Commentarii mathematici Helvetici}, volume = {61}, year = {1986}, pages = {122-148}, zbl = {0611.57015}, url = {http://dml.mathdoc.fr/item/GDZPPN002066076} }
Hillman, Jonathan A. Abelian normal subgroups of two-knot groups.. Commentarii mathematici Helvetici, Tome 61 (1986) pp. 122-148. http://gdmltest.u-ga.fr/item/GDZPPN002066076/