Fix typo in train split name (#3751)

* Fix typo in README guide

* Fix split naming and table alignment in README guide

* Fix split naming and table alignment in all datasets

* Fix previously malformed dataset cards

* Fix previously malformed dataset cards

Commit from https://github.com/huggingface/datasets/commit/af6e54febe3b822118dfed28ddb797d8350e5d27

README.md

@@ -95,9 +95,9 @@ The text in the dataset is in English
 
 The data is split into a training, validation and test.
 
-| Tain   | Valid | Test |
-| ------ | ----- | ---- |
-| 30369  |  5066 | 5093 |
+| train | validation | test |
+|------:|-----------:|-----:|
+| 30369 |       5066 | 5093 |
 
 
 ## Dataset Creation
@@ -156,7 +156,14 @@ The data is split into a training, validation and test.
 
 ### Citation Information
 
-[More Information Needed]
+```
+@article{lu2020multi,
+  title={Multi-XScience: A Large-scale Dataset for Extreme Multi-document Summarization of Scientific Articles},
+  author={Lu, Yao and Dong, Yue and Charlin, Laurent},
+  journal={arXiv preprint arXiv:2010.14235},
+  year={2020}
+}
+```
 
 ### Contributions