@article{JRAM_1997__485_183542,
     author = {Alexandru Buium},
     title = {Differential characters and characteristic polynomial of {Frobenius.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {209--219},
     publisher = {mathdoc},
     volume = {485},
     year = {1997},
     zbl = {0871.14035},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1997__485_183542/}
}