K. M. Koh, T. Tan, D. G. Rogers. Two theorems on graceful trees. Discrete Mathematics, 25(2):141-148, 1979. [doi]
@article{KohTR79,
title = {Two theorems on graceful trees},
author = {K. M. Koh and T. Tan and D. G. Rogers},
year = {1979},
doi = {10.1016/0012-365X(79)90016-5},
url = {http://dx.doi.org/10.1016/0012-365X(79)90016-5},
researchr = {https://researchr.org/publication/KohTR79},
cites = {0},
citedby = {0},
journal = {Discrete Mathematics},
volume = {25},
number = {2},
pages = {141-148},
}