Sandeep N. Bhatt Shimon Even David S. Greenberg Rafi Tayar Traversing Directed Eulerian Mazes. 157-173 2002 6 J. Graph Algorithms Appl. 2 http://www.cs.brown.edu/publications/jgaa/accepted/2002/Bhatt+2002.6.2.pdf db/journals/jgaa/jgaa6.html#BhattEGT02