@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/