@article{10_37236_1621,
     author = {Frank Van Bussel},
     title = {Relaxed graceful labellings of trees},
     journal = {The electronic journal of combinatorics},
     year = {2002},
     volume = {9},
     doi = {10.37236/1621},
     zbl = {0981.05089},
     url = {http://geodesic.mathdoc.fr/articles/10.37236/1621/}
}