@article{MS2_1974__35_166367,
     author = {Ragni Piene},
     title = {Courbes sur un trait et morphismes de contraction.},
     journal = {Mathematica Scandinavica},
     pages = {5--15},
     publisher = {mathdoc},
     volume = {35},
     year = {1974},
     zbl = {0293.14009},
     url = {http://geodesic.mathdoc.fr/item/MS2_1974__35_166367/}
}