Let be a set of s positive integers. Suppose that and are two collections of subsets of [n]={1,2,…,n} such that whenever i≠j. If the set systems satisfy one of the following conditions:
(1) implies Ai=Bi
(2) Ai∩Bj≤Aj∩Bj with equality possible only when Ai∩Bi>Aj∩Bj for i≠j, then we bound m as This result extends Snevily’s theorem to cross -intersecting two families.