Update dataset card with citation

README.md

@@ -1,8 +1,22 @@
 ---
 license: mit
+arxiv: 2603.15617
 configs:
   - config_name: default
     data_files:
       - split: test
         path: data/problems_full.json
----
+---
+
+## Citation
+```bibtex
+@article{wang2026horizonmathmeasuringaiprogress,
+      title={HorizonMath: Measuring AI Progress Toward Mathematical Discovery with Automatic Verification}, 
+      author={Erik Y. Wang and Sumeet Motwani and James V. Roggeveen and Eliot Hodges and Dulhan Jayalath and Charles London and Kalyan Ramakrishnan and Flaviu Cipcigan and Philip Torr and Alessandro Abate},
+      year={2026},
+      eprint={2603.15617},
+      archivePrefix={arXiv},
+      primaryClass={cs.LG},
+      url={https://arxiv.org/abs/2603.15617}, 
+}
+```