1. Lect. Notes Comput. Sci.;I. Bárány,2001
2. Brass, P., Moser, W., Pach, J.: Research Problems in Discrete Geometry. Springer, New York (2005)
3. Erdős, P.: Some more problems on elementary geometry. Aust. Math. Soc. Gaz. 5, 52–54 (1978)
4. Colloq. Math. Soc. János Bolyai;P. Erdős,1981
5. Erdős, P., Szekeres, G.: A combinatorial problem in geometry. Compos. Math. 2, 463–470 (1935)