@article{JRAM_1982__334_152450,
     author = {Keiichi Oshikawa},
     title = {On formal groups over complete discrete valuation rings with application to a theorem of {Lutz.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {79--90},
     publisher = {mathdoc},
     volume = {334},
     year = {1982},
     zbl = {0478.14036},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1982__334_152450/}
}