# Pach, János

## Odd-cycle transversal in triangle-free graphs ★★

Author(s): Erdos; Faudree; Pach; Spencer

**Conjecture**If is a simple triangle-free graph, then there is a set of at most edges whose deletion destroys every odd cycle.

Keywords:

## Are different notions of the crossing number the same? ★★★

**Problem**Does the following equality hold for every graph ?

The crossing number of a graph is the minimum number of edge crossings in any drawing of in the plane. In the *pairwise crossing number* , we minimize the number of pairs of edges that cross.

Keywords: crossing number; pair-crossing number