The Mordell-Weil groups of unirational quasi-elliptic surfaces in characteristic 3 (Q811599)

The Mordell-Weil groups of quasi-elliptic surfaces are defined as in the case of elliptic surfaces and shown to be finitely generated torsion groups. They are described completely in the case of unirational quasi- elliptic surfaces of rational type or K3 type in characteristic 3. Moreover, the lattice structures of the Néron-Severi groups of quasi- elliptic K3 surfaces in characteristic 3 are determined.