it's just my style
If you really need to dig down into a particular subject, access underground search engines that are not as well known, dig much more deeply into specialized areas of the Internet than the general search engines are capable of.
The Invisible Web refers to the part of the WWW that’s not indexed by the search engines. Most of us think that that search engines see everything. Unfortunately, they can’t because they are just web spiders who index pages by following one hyperlink after the other.
But there are some places where a spider cannot enter. Saikat shows you ten search engines that help you explore that “invisible web”.
Read about them here 10 Search Engines to Explore the Invisible Web.