[ubuntu-uk] Duplicate sources list

[scoundrel50a]

I use the terminal to update and dist upgrade, and since I reinstalled 
my kernal, I now have duplicate sources.list errors showing which stop 
the terminal from  updating, it tells me in the panel that there updates 
but I can only update using update manager.....

this is one of the errors

W: Duplicate sources.list entry http://archive.ubuntu.com/ubuntu/ 
precise/universe amd64 Packages 
(/var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_precise_universe_binary-amd64_Packages)

There is about a dozen of them, which one is the duplicate and which one 
can Iget rid of and how......

thanks