Marc Noy. Acyclic and Totally Cyclic Orientations in Planar Graphs. The American Mathematical Monthly, 108(1):66-68, 2001. [doi]
@article{Noy01, title = {Acyclic and Totally Cyclic Orientations in Planar Graphs}, author = {Marc Noy}, year = {2001}, url = {http://www.jstor.org/stable/2695680}, researchr = {https://researchr.org/publication/Noy01}, cites = {0}, citedby = {0}, journal = {The American Mathematical Monthly}, volume = {108}, number = {1}, pages = {66-68}, }