Integer difference covers which are not k-sum covers, for k = 6, 7
Dennis Connolly · Mathematical Proceedings of the Cambridge Philosophical Society · 1973
Constructions are given of sets F(k), (k = 6, 7) of residues mod q(k), (for a suitably chosen integer q(k)) such that F(k) – F(k) contains all residues, while has a gap of an assigned number of consecutive residues.