Add published reference citation (instead of preprint)

README.md

@@ -322,10 +322,11 @@ If you use this model in your research, please cite both it and the source model
     title = "Sentence-BERT: Sentence Embeddings using Siamese BERT-Networks",
     author = "Reimers, Nils and Gurevych, Iryna",
     booktitle = "Proceedings of the 2019 Conference on Empirical Methods in Natural Language Processing",
-    month = "11",
+    month = "01",
     year = "2019",
+    pages = "3973-3983",
     publisher = "Association for Computational Linguistics",
-    url = "https://arxiv.org/abs/1908.10084",
+    doi = "10.18653/v1/D19-1410"
 }
 ```