1.
Shapira A. Every Orientation of a $4$-Chromatic Graph has a Non-Bipartite Acyclic Subgraph. Electron. J. Combin. [Internet]. 2022Jan.28 [cited 2026Mar.29];29(1):P1.2. Available from: https://www.combinatorics.org/ojs/index.php/eljc/article/view/v29i1p2