[](https://js.langchain.com/docs/how_to/query_multiple_retrievers/): LLM should read this page when: 1) Handling queries that require retrieving information from multiple data sources, 2) Building a question answering system that needs to dynamically select the appropriate retriever based on the query, 3) Integrating multiple retrieval mechanisms into a single application. The page explains how to perform query analysis to determine which retriever to use for a given query, and then how to dynamically select and invoke the appropriate retriever based on the query analysis result.

