@article{MZ_1985__189_173573,
     author = {Harry A.W.M. Kneppers},
     title = {The {Hasse-Witt} {Matrix} of a {Formal} {Group.}},
     journal = {Mathematische Zeitschrift},
     pages = {151--166},
     year = {1985},
     volume = {189},
     zbl = {0535.14021},
     url = {http://geodesic.mathdoc.fr/item/MZ_1985__189_173573/}
}