@INPROCEEDINGS{LeBras2013Double,
  title={Double-Wheel Graphs Are Graceful},
  author={Le Bras, Ronan and Gomes, Carla P and Selman, Bart},
  booktitle = {Proceedings of the 23rd International Joint Conference on Artificial Intelligence}, 
  year = {2013}, series = {IJCAI'13}, 
  location = {Beijing, China}
}