How to replace part of text in Emacs with a link or link?

Question

When writing letters using Emacs, I like to use this format with numbers between square brackets to point to URLs.

Example:

The first version [1] is still buggy, so I downloaded SomeAlternative [2].

[1]: http://blahblahahlahblah.com/version1

[2]: http://gaaaaaaaah.com/

Is there any Emacs mode or key sequence that allows me to quickly replace a URL with a link in this format?

Answer 1

There is an original footnote-mode small mode.

Answer 2

org-mode will do this.