added note about the European Open Source AI Index

models.md

@@ -151,6 +151,9 @@ window, improved tool use, and instruction-following. It's the *publicly
 developed* counterpart to the private (Tinfoil) and renewable (GreenPT)
 offerings — sovereignty as a third axis of member choice.
 
+For more information on open-source AI and the Apertus models, see the
+[European Open Source AI Index](https://osai-index.eu/database/).
+
 *Source: [apertus-ai.org](https://www.apertus-ai.org/) and the
 [Swiss AI Hugging Face](https://huggingface.co/swiss-ai) model cards.*