Update citation information

README.md

@@ -174,9 +174,35 @@ Computational Use of Data Agreement (C-UDA) License.
 ### Citation Information
 
 ```
-@article{CodeXGLUE,
-         title={CodeXGLUE: A Benchmark Dataset and Open Challenge for Code Intelligence},
-         year={2020},}
+@article{DBLP:journals/corr/abs-2102-04664,
+  author    = {Shuai Lu and
+               Daya Guo and
+               Shuo Ren and
+               Junjie Huang and
+               Alexey Svyatkovskiy and
+               Ambrosio Blanco and
+               Colin B. Clement and
+               Dawn Drain and
+               Daxin Jiang and
+               Duyu Tang and
+               Ge Li and
+               Lidong Zhou and
+               Linjun Shou and
+               Long Zhou and
+               Michele Tufano and
+               Ming Gong and
+               Ming Zhou and
+               Nan Duan and
+               Neel Sundaresan and
+               Shao Kun Deng and
+               Shengyu Fu and
+               Shujie Liu},
+  title     = {CodeXGLUE: {A} Machine Learning Benchmark Dataset for Code Understanding
+               and Generation},
+  journal   = {CoRR},
+  volume    = {abs/2102.04664},
+  year      = {2021}
+}
 ```
 
 ### Contributions