More missing entries in Lander's table could be filled (Q580346)

By proving a lemma on intersection numbers of a difference set relative to a subgroup of the underlying group, we prove the nonexistence of six difference sets, without the aid of an electronic device. We also exhibit (63,28,12) difference sets in \(Z_ 8\times Z_ 8\) and \(Z_ 4\times Z_{16}\). Thus eight more missing entries in Lander's table can be filled, six with answer ''no'' and two with ''yes''.