Add paper arXiv URL to dataset card

README.md

@@ -111,6 +111,7 @@ configs:
 
 - **Repository:** [ASSET Github repository](https://github.com/facebookresearch/asset)
 - **Paper:** [ASSET: A Dataset for Tuning and Evaluation of Sentence Simplification Models with Multiple Rewriting Transformations](https://www.aclweb.org/anthology/2020.acl-main.424/)
+- **Paper:** https://arxiv.org/abs/2005.00481
 - **Point of Contact:** [Louis Martin](louismartincs@gmail.com)
 
 ### Dataset Summary