Weakly union-free twofold triple systems
The authors settle the problem of Frankl and Füredi (a special case of a problem of Erdős) which is to determine the maximum number of edges in a 3-uniform hypergraph in which no two pairs of distinct edges have the same union. The extremal case corresponds to the question of existence of weakly union-free twofold triple systems; this question is given a complete answer up to four possible exceptions. An application to group testing is also given.
scientific article; zbMATH DE number 1160053