Update README.md

Author: paatai

README.md

@@ -105,7 +105,7 @@ We are arbitrarily numbering the constants as $C_{1}$, $C_{2}$, etc., mostly bas
 
 ## Recent progress
 
-- [11b](https://teorth.github.io/optimizationproblems/constants/11b.html) **solved:** $C_{11b} = 0.5$ by  [P. Durcik, P. Ivanisvili, J. Roos, X. Xie](https://arxiv.org/abs/2602.20462).
+- [11b](https://teorth.github.io/optimizationproblems/constants/11b.html) **solved:** $C_{11b} = 0.5$ by  [P. Durcik, P. Ivanisvili, J. Roos, X. Xie](https://arxiv.org/abs/2602.20462), 24 Feb 2026.
 - [3c](https://teorth.github.io/optimizationproblems/constants/3c.html) **improved lower bound:** $C_{3c} \geq 1.67471$ by T. Astor (paper coming soon).
 - [51](https://teorth.github.io/optimizationproblems/constants/51a.html) **improved lower bound:** $C_{51} \geq 0.58507$ by [Y. He and Q. Tang](https://arxiv.org/abs/2602.12217), 12 Feb 2026.