Update Readme.md

Author: Messi-Q

Readme.md

@@ -36,5 +36,5 @@ The train data after normalization:
 
 
 ### Reference
-1. The code borrows from [Graph_unet](https://github.com/bknyaz/graph_nn)
+1. The code borrows from [graph_unet](https://github.com/bknyaz/graph_nn)
 2. Thomas N. Kipf, Max Welling, Semi-Supervised Classification with Graph Convolutional Networks, ICLR 2017