Card: link WildAI (code and paper) and add its citation

README.md

@@ -98,7 +98,8 @@ The paraphrase keeps every item's role, order and content, and changes only the
 ## How the corpus was built
 
 - **Documents and labels.** Documents are English Common Crawl pages from the 2024, 2025 and 2026 crawls, drawn from
-  the WildAI corpus, which builds on FineWeb and annotates each page with a WebOrganizer format and topic and a
+  the [WildAI](https://github.com/pangramlabs/WildAI) corpus ([Russell et al., 2026](https://arxiv.org/abs/2609.40295)),
+  which builds on FineWeb and annotates each page with a WebOrganizer format and topic and a
   Pangram authorship prediction. We kept documents of at least 500 words, in eight long-form formats, that Pangram
   labels as entirely human-written or entirely AI-generated. Documents Pangram labels as mixed or AI-assisted were left
   out. The paper describes the construction in full.
@@ -172,3 +173,15 @@ with Google Gemini models.
   url     = {https://arxiv.org/abs/TBD}
 }
 ```
+
+The documents come from WildAI; if you use them, please also cite:
+
+```bibtex
+@article{russell2026wildai,
+  title   = {How Much Is an AI Token Worth? Scaling Laws for Wild AI-Generated Web Text},
+  author  = {Russell, Jenna and Glickenhaus, Ben and Thai, Katherine and Wieting, John and Iyyer, Mohit and Spero, Max and Emi, Bradley},
+  journal = {arXiv preprint arXiv:2609.40295},
+  year    = {2026},
+  url     = {https://arxiv.org/abs/2609.40295}
+}
+```