On the Covariant Dieudonné-Module of an Abelian Variety of Dimension Two over W(k). Bert (E.J. Ditters — 1981 Mathematische Zeitschrift
On the Connected Part of the Covariant Tate p-divisible Group and the ?-function of the Family of Hyperelliptic Curves y2 = 1 + ? xN Modulo Various Primes. Bert (E.J. Ditters; Simen J. Hoving Mathematische Zeitschrift