11.04 - I need the default set of software sources to recover my installation

I just had the default ones. They are ALL gone. I can't install any software at all. I am using Kubuntu 11.04 x86.

I have no idea why they disappeared. They just did. :/

How do I get the default software sources back?

(I know the sudo add-apt-repository command, but I need to names of the default repositories)