http://tenchan4v5bnlu3gatyjyctlsb25asvncbz4pr7gmomhsrvyx5zfpcad.onion/res/348.html
It's very useful in OSINT, and also if you're a student looking for research papers. Just search up, google dorking techniques, and learn the symbols and keywords that you can use to fine tune your search. I think other search engines have something similar to this as well.