@article{10_4153_CJM_1987_015_5,
     author = {Fenn, Roger and Sjerve, Denis},
     title = {Massey {Products} and {Lower} {Central} {Series} of {Free} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {322--337},
     year = {1987},
     volume = {39},
     number = {2},
     doi = {10.4153/CJM-1987-015-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1987-015-5/}
}