Does placing links to related sites improve rankings?

[BloodNinja3]

Does placing links to related sites improve rankings?

As google says that their motive is to provide better information to people, I think they give weightage to links to related sites as well.

For example many pages in wikipedia have links to .gov or .edu sites like say 20 links per page. This is because wikipedia tries to provide more info to people. And the pages rank well.

Has this something to do with the .edu or .gov links on the pages? I know that wikipedia has many back links but I still wonder if the .edu or .gov links have something to do with it.