apt - Can someone provide a real, correct and genuine sources.list for Ubuntu 15.04?

I have been using Ubuntu for a while now and I have been having all problems that I needed not to post a thread for to get answers, until I recently upgraded to Ubuntu Vivid.

Ubuntu is great but each time I run sudo apt-get update I have a smooth run of update which return a notice of a duplicate in /var/lib/apt/lists.

That is not even where the problem lies. What is very frustrating is that even when I run the proposed update, it still produces the same result.

I was using Ubuntu 14.04 then I upgraded to Ubuntu Utopic before upgrading to Vivid.

All I need is someone to please provide a compact without duplicates source list.

Please.

Thank you all in advance.

Edit: This is the new error I got from reloading the software-properties-gtk.

W: Duplicate sources.list entry http://security.ubuntu.com/ubuntu/ vivid-security/restricted i386 Packages (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_vivid-security_restricted_binary-i386_Packages)

W: Duplicate sources.list entry http://security.ubuntu.com/ubuntu/ vivid-security/universe i386 Packages (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_vivid-security_universe_binary-i386_Packages)
W: Duplicate sources.list entry http://security.ubuntu.com/ubuntu/ vivid-security/multiverse i386 Packages (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_vivid-security_multiverse_binary-i386_Packages)
W: Duplicate sources.list entry http://security.ubuntu.com/ubuntu/ vivid-security/main i386 Packages (/var/lib/apt/lists/security.ubuntu.com_ubuntu_dists_vivid-security_main_binary-i386_Packages)
W: You may want to run apt-get update to correct these problems