On Gracefulness of Directed Trees with Short Diameters
Malaysian Mathematical, Bing Yao, Yao Ming, Hui Dong Cheng · 2012
Graceful labelling is studied on undirected graphs since graceful graphs can be used in some H-decomposition problems. In this note, we inves- tigate the directed graceful problem for many orientations of undirected trees with short diameters, and provide some directed trees that deny any digraceful labelling.