Update README.md

README.md

@@ -9,6 +9,12 @@ Details about the dataset can be found in the original paper:
   [Deep keyphrase Generation](https://aclanthology.org/P17-1054.pdf)
   Proceedings of the 55th Annual Meeting of the Association for Computational Linguistics, pages 582–592
   
+Reference (indexer-assigned) keyphrases are also categorized under the PRMU (<u>P</u>resent-<u>R</u>eordered-<u>M</u>ixed-<u>U</u>nseen) scheme as proposed in the following paper:
+ - Florian Boudin and Ygor Gallina. 2021.
+   [Redefining Absent Keyphrases and their Effect on Retrieval Effectiveness](https://aclanthology.org/2021.naacl-main.330/). 
+   In Proceedings of the 2021 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, pages 4185–4193, Online. Association for Computational Linguistics.
+   
+  
 ## Content
 
 The dataset is divided into the following three splits:
@@ -21,7 +27,7 @@ The dataset is divided into the following three splits:
 
 
 The following data fields are available:
-- **id**: unique identifier of the document.
+- **id**: unique identifier of the document. **NB** There were no ids in the original dataset. The ids were generated using the python module shortuuid (https://pypi.org/project/shortuuid/)
 - **title**: title of the document.
 - **abstract**: abstract of the document.
 - **keyphrases**: list of reference keyphrases.