![](/files/happy5.png)
Conjecture If
is a simple triangle-free graph, then there is a set of at most
edges whose deletion destroys every odd cycle.
![$ G $](/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png)
![$ n^2/25 $](/files/tex/0db5eaf8ff84c2da58a206455442346f6fa11c19.png)
Bibliography
*[EFPS] P. Erdös, R. Faudree, J. Pach and J. Spencer, How to make a graph bipartite. J. Combin. Theory Ser. B 45 (1988), 86--98.
* indicates original appearance(s) of problem.