@article{CLTM_1964_1964_1_a11,
     author = {Pascual, Griselda},
     title = {Estructuras circulares y su orientaci\'on.},
     journal = {Collectanea mathematica},
     publisher = {mathdoc},
     number = {2-3},
     year = {1964},
     language = {es},
     url = {http://geodesic.mathdoc.fr/item/CLTM_1964_1964_1_a11/}
}