# Is the graceful labeling conjecture still unsolved?

From the Wikipedia article on graceful labeling:

... A major unproven conjecture in graph theory is the Ringel–Kotzig conjecture, named after Gerhard Ringel and Anton Kotzig, which hypothesizes that all trees are graceful. The Ringel-Kotzig conjecture is also known as the "graceful labeling conjecture". ...

Is the conjecture still unsolved?

(for example I found Dhananjay P. Mehendale, "On Gracefully Labeling Trees", which claims that the conjecture is true).

• See the latest version at arxiv.org/ftp/math/papers/0503/0503484.pdf you are refering to old version. – user73830 Apr 22 '13 at 17:06
• I've already said this somewhere, but you should take any math paper not written in TeX with an additional dose of suspicion. – tomasz Jul 6 '13 at 14:29
• the definition of graceful labeling is wrong in the referred paper – vidyarthi Apr 16 at 14:32