Blocking sets in G-designs and K3,3 - designs

Abstract

The problem to determine the existence of possible blocking sets in Steiner systems has been studied by many authors from many points of view and there is a big literature about it (see references). In this paper, some general results about the existence of blocking sets in G-designs are given. In particular blocking sets of all possible sizes in K3,3 - designs of order 19 are determined.