Update README.md

I added the url of the source code.

README.md

@@ -9,12 +9,10 @@ The detailed implementation of the model can be found in:
 
 https://arxiv.org/pdf/2112.08185.pdf
 
-Source code to train the model can be found in:
-```
-To be updated. 
-```
+Source code to train the model can be found via PrimeQA's IR component:
+https://github.com/primeqa/primeqa/tree/updated-documentation-readme/primeqa/ir/dense/colbert_top
 
-It is a Neural IR model therefore not directly compatible with Huggingface API. The inference result on XOR Dev dataset is:
+It is a Neural IR model built on top of the ColBERTv1 api and not directly compatible with Huggingface API. The inference result on XOR Dev dataset is:
 ```
    	R@2kt	R@5kt
  te	79.41	83.19