Added link to paper and bibtex to README (#18)

README.md

@@ -1,5 +1,6 @@
 # GEOUNED
 A tool to convert from CAD to CSG & CSG to CAD for Monte Carlo transport codes (MCNP & OpenMC).
+This repository contains the implementation of the algorithm presented in the paper [GEOUNED: A new conversion tool from CAD to Monte Carlo geometry](https://doi.org/10.1016/j.net.2024.01.052).
 
 ## Installation 
 
@@ -73,4 +74,17 @@ linux (forward and reverse):
 /~>geouned -r file_config_name
 ```
 
-Detailed descriptions of all options of the config files (forward ans reverse) are given in the manual located in ~docs/ folder.
+Detailed descriptions of all options of the config files (forward ans reverse) are given in the manual located in ~docs/ folder.
+
+## Citation
+
+```
+@article{CATALAN2024,
+  author = {J.P. Catalán and P. Sauvan and J. García and J. Alguacil and F. Ogando and J. Sanz},
+  title = {GEOUNED: A new conversion tool from CAD to Monte Carlo geometry},
+  journal = {Nuclear Engineering and Technology},
+  year = {2024},
+  issn = {1738-5733},
+  doi = {https://doi.org/10.1016/j.net.2024.01.052}
+}
+```