If you need to validate the sources, you might as well go to the sources directly and bypass the LLM. The whole point of LLMs is not needing to go to the sources. The LLM consumes them for you. If you need to read and understand the sources yourself well enough to tell if the LLM is lying, the LLM is a wasteful middleman.

It's like buying supermarket food and also buying the same food from the farmers themselves.