@article{GDZPPN002347326,
title = {Length Functions in Groups.},
journal = {Mathematica Scandinavica},
volume = {13},
year = {1963},
pages = {209-234},
zbl = {0119.26402},
url = {http://dml.mathdoc.fr/item/GDZPPN002347326}
}
Lyndon, Roger C. Length Functions in Groups.. Mathematica Scandinavica, Tome 13 (1963) pp. 209-234. http://gdmltest.u-ga.fr/item/GDZPPN002347326/