@article{10_4064_fm_163_3_229_239,
     author = {Jianwei Song and E. D. Tymchatyn},
     title = {Free spaces},
     journal = {Fundamenta Mathematicae},
     pages = {229--239},
     publisher = {mathdoc},
     volume = {163},
     number = {3},
     year = {2000},
     doi = {10.4064/fm-163-3-229-239},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-163-3-229-239/}
}