Graceful umbrella trees
Zhen-Bin Gao · Journal of Natural Science of Heilongjiang University · 2003
Along with the development of computer, the sign of graphs is becoming popular on internet and in communication. Mr.A.Rosa had one idea that every tree is graceful. Mr. Gnanajothi had another ideathat every tree is odd graceful. It is discussed that a group of trees is graceful and odd graceful.