Update README.md

README.md

@@ -69,3 +69,11 @@ This repository makes use of the following published codes:
 - K. Altenmuller et al, REST-for-Physics, a ROOT-based framework for event oriented data analysis and combined Monte Carlo response, [Computer Physics Communications 273, April 2022, 108281](https://doi.org/10.1016/j.cpc.2021.108281).
 - S.Hoof, J.Jaeckel, T.J.Lennert, Quantifying uncertainties in the solar axion flux and their impact on determining axion model parameters, [JCAP09(2021)006](https://doi.org/10.1088/1475-7516/2021/09/006).
 - T.Kittelmann, E.Klinkby, E.B.Knudsen, P.Willendrup, X.X.Cai, K.Kanaki, Monte Carlo Particle Lists: MCPL, Computer Physics Communications 218 (2017) 17–42](http://dx.doi.org/10.17632/cby92vsv5g.1).
+
+### License
+
+**axionlib** is distributed under a [Creative Commons license](https://creativecommons.org/licenses/).
+If you use or adapt any of the code in this repository, please cite the following work:
+
+ **IAXO Collaboration**, Ahyoune, S., Altenmüller, K. et al., “An accurate solar axions ray-tracing response of BabyIAXO.”
+ *Journal of High Energy Physics* **2025**, 159 (2025). [https://doi.org/10.1007/JHEP02(2025)159](https://doi.org/10.1007/JHEP02(2025)159)