@article{JRAM_1997__484_153898,
     author = {Bernard M. Dwork},
     title = {On exponents of p-adic differential modules.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {85--126},
     publisher = {mathdoc},
     volume = {484},
     year = {1997},
     zbl = {0870.12008},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1997__484_153898/}
}