Ubuntu 16.04 not updating past version 4.0.9-16

Hi,

I'd like to upgrade to a later version, but sudo apt-get update, upgrade and dist-upgrade don't give ma any updates. The repo in my sources.list is

The machine has an AMD 64 bit processor in it.

How can I get a later version please?

That is the latest stable version, If you want 4.1, use unstable instead.

Thanks for the reply. I've changed the sources.list entry for one of the unstable ones and it's all upgraded and working :)