• The existence of planar hypotraceable oriented graphs 

      Van Aardt, Susan A.; Burger, Alewyn Petrus; Frick, Marietjie (Discrete Mathematics & amp; Theoretical Computer Science, 2017)
      A digraph is \emph{traceable} if it has a path that visits every vertex. A digraph D is \emph{hypotraceable} if D is not traceable but D−v is traceable for every vertex v∈V(D). It is known that there exists a planar ...