Eckhardt, U. (Inst. fuer Angewandte Math., Hamburg Univ., West Germany) Maderlechner, G

There exist very complex sets that contain interior points and that are irreducible under thinning. The authors investigate the structure of such irreducible sets. It is shown that irreducible sets containing interior points have essentially the structure of a counterexample given by C. Arcelli (1981). Finally the question is raised of under which conditions irreducible sets that have a large kernel of interior points are not possible. It turns out that a very simple condition will suffice