@article{ADM_2002_1_a7,
     author = {I. V. Protasov},
     title = {Metrizable ball structures},
     journal = {Algebra and discrete mathematics},
     pages = {129--141},
     year = {2002},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ADM_2002_1_a7/}
}