A conjecture of Grünbaum on common transversals.
A Helly number for unions of two boxes in .
A New Step in the Solution of the Szökefalvi-Nagy Problem.
A Proof of Bárány's Theorem
A purely combinatorial proof of the Hadwiger Debrunner conjecture.
A sandwich theorem and Hyers-Ulam stability of affine functions.
A selection theorem of Helly type and its applications
We prove an abstract selection theorem for set-valued mappings with compact convex values in a normed space. Some special cases of this result as well as its applications to separation theory and Hyers-Ulam stability of affine functions are also given.
A simple geometrie proof of a theorem for starshaped unions of convex sets
A staircase illumination theorem for orthogonal polygons.