A note on difference sets
Let \(G\) be a group not necessary abelian, and \(N\) a normal subgroup of \( G\). Suppose there is a \((v,k,\lambda)\)-DS in \(G\). Bounds on \(| N| \) and \(\lambda\) are given in terms mainly of \(k-\lambda\) under (strong) assumptions on the structure and the order of \(G/N\) using group rings. The results are applicable to a wide variety of parameters; so there exists no \((26,20,4)\)-DS in \(C_4\times C_8\times C_3\) and in \(C_2\times C_2\times C_8\times C_3\).
scientific article; zbMATH DE number 1236147