Sets without emtpy convex 6-gons

@article{Overmars1989SetsWE,
  title={Sets without emtpy convex 6-gons},
  author={Mark H. Overmars and Bertha Scholten and Ingrid Vincent},
  journal={Bulletin of the EATCS},
  year={1989},
  volume={37},
  pages={160-167}
}