How do I implement getting real sources from my mini search engine?

Being inspired from a reddit post I'm trying to build a mini search engine(https://kolpz.vercel.app) that gives user exactly what it needs. Concise and straightforward results. I implemented prefixes feature like define, question, pdf, time, weather. For now I added these 5 prefixes. But for the pdf prefix, I want it to give direct pdf download links for the asked book or research paper. I made a very concise prompt for it too. Exactly mentioned which sources to use to find the books or papers for free. But it's generating(Gemini API) totally made up links. Not even a single link is real.

I want to get real source links. How can I do it with Gemini AI? What additional API's can I use to make this happen?

(Reducing the temperature doesn't work that well either)