@article{MAN_1970__186_161990,
     author = {S.J. BERNAU},
     title = {Free {Non-abelian} {Lattice} {Groups.}},
     journal = {Mathematische Annalen},
     pages = {249--262},
     publisher = {mathdoc},
     volume = {186},
     year = {1970},
     zbl = {0185.07501},
     url = {http://geodesic.mathdoc.fr/item/MAN_1970__186_161990/}
}