@article{JRAM_1962__210_150540,
     author = {Roger C. Lyndon},
     title = {Dependence and {Independence} in {Free} {Groups.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {148--174},
     publisher = {mathdoc},
     volume = {210},
     year = {1962},
     zbl = {0105.01901},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1962__210_150540/}
}