@article{JRAM_1992__425_153396,
     author = {F. Acquistapace and F. Broglia},
     title = {Signatures and flatness.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {61--70},
     publisher = {mathdoc},
     volume = {425},
     year = {1992},
     zbl = {0758.14041},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1992__425_153396/}
}