1561 References Cited U.S. PATENT DOCUMENTS 3,792,423 2/1974 Becker et al. ......................... 73/620 3,979,712 9/1976 Ettenhofer et al. . 4,028,934 6/1977 Sollish ................................... 73/620 4,327,576 5/1982 Dickey et al. ................... 73/40.5 A 4,640,121 2/1987 Leuker et al. ................... 73/40.5 A 4,641,526 2/1987 Izumi et al. ........................... 73/5...

Nikulin has classified all finite abelian groups acting symplectically on a K3 surface and he has shown that the induced action on the K3 lattice U⊕E8(−1) depends only on the group but not on the K3 surface. For all the groups in the list of Nikulin we compute the invariant sublattice and its orthogonal complement by using some special elliptic K3 surfaces.