Diestel, Reinhard (2010), Graph Theory (4th ed.), Berlin, New York: Springer-Verlag, pp. 169–198, ISBN978-3-642-14278-9, archived from the original on 2017-05-28, retrieved 2013-11-18
Diestel, Reinhard (2010), Graph Theory (4th ed.), Berlin, New York: Springer-Verlag, pp. 169–198, ISBN978-3-642-14278-9, archived from the original on 2017-05-28, retrieved 2013-11-18