Update README.md

cookbook/pocketflow-rag/README.md

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 # Retrieval Augmented Generation (RAG)
 
-This project demonstrates a simplified RAG system that retrieves relevant documents based on user queries and generates answers using an LLM.
+This project demonstrates a simplified RAG system that retrieves relevant documents based on user queries and generates answers using an LLM. This implementation is based directly on the tutorial: [Retrieval Augmented Generation (RAG) from Scratch — Tutorial For Dummies](https://zacharyhuang.substack.com/p/retrieval-augmented-generation-rag).
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 ## Features
 
@@ -69,4 +70,4 @@ Here's what each part does:
 
 🤖 Generated Answer:
 To install PocketFlow, use the command `pip install pocketflow` or simply copy its 100 lines of source code.
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+```