On a generalization of Deuring's results
  Using the Dieudonne theory we will study a reduction of an abelian variety of complex multiplication. Our results may be regarded as a generalization of a classical theorem due to Deuring for a CM-elliptic curve. We will also discuss a sufficient condition that is a proper smooth curve with CM to be maximal. 
Ken-ichi Sugiyama
math.NT math.AG