Add citation bibtex.

README.md

@@ -39,3 +39,23 @@ We encourage you to use the [beginner's tutorial](https://colab.research.google.
 - [**Training**](docs/training.md)
 - [**Prediction**](docs/prediction.md)
 - [**Model performance**](docs/performance.md)
+
+## Citing
+
+If you use EUD in your research, please cite [COMBO: A New Module for EUD Parsing](https://aclanthology.org/2021.iwpt-1.16/)
+```bibtex
+@inproceedings{klimaszewski-wroblewska-2021-combo,
+    title = "{COMBO}: A New Module for {EUD} Parsing",
+    author = "Klimaszewski, Mateusz  and
+      Wr{\'o}blewska, Alina",
+    booktitle = "Proceedings of the 17th International Conference on Parsing Technologies and the IWPT 2021 Shared Task on Parsing into Enhanced Universal Dependencies (IWPT 2021)",
+    month = aug,
+    year = "2021",
+    address = "Online",
+    publisher = "Association for Computational Linguistics",
+    url = "https://aclanthology.org/2021.iwpt-1.16",
+    doi = "10.18653/v1/2021.iwpt-1.16",
+    pages = "158--166",
+    abstract = "We introduce the COMBO-based approach for EUD parsing and its implementation, which took part in the IWPT 2021 EUD shared task. The goal of this task is to parse raw texts in 17 languages into Enhanced Universal Dependencies (EUD). The proposed approach uses COMBO to predict UD trees and EUD graphs. These structures are then merged into the final EUD graphs. Some EUD edge labels are extended with case information using a single language-independent expansion rule. In the official evaluation, the solution ranked fourth, achieving an average ELAS of 83.79{\%}. The source code is available at https://gitlab.clarin-pl.eu/syntactic-tools/combo.",
+}
+```