@article{10_4064_fm226_1_2,
     author = {Jeremy Brazas},
     title = {Open subgroups of free topological groups},
     journal = {Fundamenta Mathematicae},
     pages = {17--40},
     publisher = {mathdoc},
     volume = {226},
     number = {1},
     year = {2014},
     doi = {10.4064/fm226-1-2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm226-1-2/}
}