  This paper classifies Enriques surfaces whose K3-cover is a fixed
Picard-general Jacobian Kummer surface. There are exactly 31 such surfaces. We
describe the free involutions which give these Enriques surfaces explicitly. As
a biproduct, we show that Aut(X) is generated by elements of order 2, which is
an improvement of the theorem of S. Kondo.
