@article{MZ_1992__209_2_174376,
     author = {Louis J. Billera and Lauren L. Rose},
     title = {Modules of piecewise polynomials and their freeness.},
     journal = {Mathematische Zeitschrift},
     pages = {485--498},
     publisher = {mathdoc},
     volume = {209},
     number = {2},
     year = {1992},
     zbl = {0891.13004},
     url = {http://geodesic.mathdoc.fr/item/MZ_1992__209_2_174376/}
}