add suggested citation and contact info

index.md

@@ -12,3 +12,11 @@ This site is the online documentation for the FeliX model. Here, we provide over
 This online documentation is prepared by
 [Quanliang Ye](https://www.ru.nl/en/people/ye-q) and [Sibel Eker](https://iiasa.ac.at/staff/sibel-eker) with contributions from [Qi Liu](https://www.researchgate.net/profile/Qi-Liu-321) and [Deepthi Swamy](https://iiasa.ac.at/staff/deepthi-swamy). 
 
+*Suggested citations*:
+- This online page: Ye, Q., Eker, S., 2024. The FeliX 2.0 webpage: overview of the underlying modeling
+methodology and links to the FeliX 2.0 resources and publications. https://iiasa.github.io/felix_docs/.
+- The FeliX methodoloy article:  Ye, Q., Liu, Q., Swamy, D., Gao, L., Moallemi, E. A., Rydzak, F., Eker, S., 2024. FeliX 2.0: An integrated model of climate, economy, environment, and society interactions. Environmental Modelling & Software 179, 106121. https://doi.org/10.1016/j.envsoft.2024.106121.
+
+*Contact Information*:
+- **Dr. Quanliang Ye**, [email protected], Nijmegen School of Management, Radboud University, 6525 XZ, Nijmegen, the Netherlands.
+- **Dr. Sibel Eker**, [email protected], Nijmegen School of Management, Radboud University, 6525 XZ, Nijmegen, the Netherlands / International Institute for Applied Systems Analysis (IIASA), Laxenburg, 2361, Austria