Fix baseline citation (Arabzadeh et al., CIKM 2021)

README.md

@@ -37,8 +37,7 @@ metrics:
 
 Adaptive routing **baseline** from **RetrievalRouter: Joint Modality and Architecture Selection
 for Document Retrieval** (EMNLP 2026). This is **not** the RetrievalRouter method — it is the
-prior strategy-selection approach of
-[Arabzadeh et al. (2021)](https://dl.acm.org/doi/10.1145/3459637.3482119), extended to our
+prior strategy-selection approach of Arabzadeh et al. (CIKM 2021), extended to our
 five-pipeline setting and trained under an identical pipeline for a controlled comparison.
 
 - 📄 Paper: https://arxiv.org/pdf/2608.23176
@@ -107,6 +106,9 @@ selected pipeline against your own indices.
 
 ## Citation
 
+If you use this baseline, please cite both the RetrievalRouter paper and the original
+strategy-selection method it is based on:
+
 ```bibtex
 @inproceedings{kuru2026retrievalrouter,
   title     = {RetrievalRouter: Joint Modality and Architecture Selection for Document Retrieval},
@@ -114,4 +116,12 @@ selected pipeline against your own indices.
   booktitle = {Proceedings of EMNLP 2026},
   year      = {2026}
 }
+
+@inproceedings{arabzadeh2021predicting,
+  title     = {Predicting efficiency/effectiveness trade-offs for dense vs. sparse retrieval strategy selection},
+  author    = {Arabzadeh, Negar and Yan, Xinyi and Clarke, Charles L. A.},
+  booktitle = {Proceedings of the 30th ACM International Conference on Information \& Knowledge Management (CIKM)},
+  pages     = {2862--2866},
+  year      = {2021}
+}
 ```