@article{BMMS_2012_35_1_a11,
     author = {Bing Yao and Ming Yao and Hui Cheng},
     title = {On {Gracefulness} of {Directed} {Trees} with {Short} {Diameters}},
     journal = {Bulletin of the Malaysian Mathematical Society},
     year = {2012},
     volume = {35},
     number = {1},
     url = {http://geodesic.mathdoc.fr/item/BMMS_2012_35_1_a11/}
}