update README.

README.md

@@ -95,4 +95,16 @@ To test the trained policy, you can input the policy checkpoint into the trainin
 python train_shac.py --cfg ./cfg/shac/ant.yaml --checkpoint ./logs/Ant/shac/policy.pt --play [--render]
 ```
 
-The `--render` flag indicates whether to export the video of the task execution. If does, the exported video is encoded in `.usd` format, and stored in the `examples/output` folder. To visualize the exported `.usd` file, refer to [USD at NVIDIA](https://developer.nvidia.com/usd).
+The `--render` flag indicates whether to export the video of the task execution. If does, the exported video is encoded in `.usd` format, and stored in the `examples/output` folder. To visualize the exported `.usd` file, refer to [USD at NVIDIA](https://developer.nvidia.com/usd).
+
+## Citation
+
+If you find our paper or code is useful, please consider citing:
+```kvk
+  @inproceedings{xu2021accelerated,
+    title={Accelerated Policy Learning with Parallel Differentiable Simulation},
+    author={Xu, Jie and Makoviychuk, Viktor and Narang, Yashraj and Ramos, Fabio and Matusik, Wojciech and Garg, Animesh and Macklin, Miles},
+    booktitle={International Conference on Learning Representations},
+    year={2021}
+  }
+```