Update the paper link

README.md

@@ -32,7 +32,7 @@ Tuned on top of Phi 4 mini
 
 Designed for multi-step, logic-intensive mathematical problem-solving tasks
 
-Find more details in their paper here: https://www.microsoft.com/en-us/research/wp-content/uploads/2025/04/phi_4_reasoning.pdf
+Find more details in their paper here: https://arxiv.org/abs/2504.21233
 
 ## Special thanks