/etc/apt/sources.list Duplicate sources.list entry

[diabolusss]

This is my /etc/apt/sources.list:

################################################## ###########
################### OFFICIAL UBUNTU REPOS ###################
################################################## ###########

###### Ubuntu Main Repos
deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted universe multiverse

###### Ubuntu Update Repos
deb http://us.archive.ubuntu.com/ubuntu/ precise-security main restricted universe multiverse
deb http://us.archive.ubuntu.com/ubuntu/ precise-updates main restricted universe multiverse

###### Ubuntu Partner Repo
deb http://archive.canonical.com/ubuntu precise partner

###### Ubuntu Extras Repo
deb http://extras.ubuntu.com/ubuntu precise main
deb http://download.virtualbox.org/virtualbox/debian precise contrib
################################################## ############
##################### UNOFFICIAL REPOS ######################
################################################## ############

###### 3rd Party Binary Repos

#### Opera - http://www.opera.com/
## Run this command: sudo wget -O - http://deb.opera.com/archive.key | sudo apt-key add -
deb http://deb.opera.com/opera/ stable non-free

When i run apt-get update i get:

Reading package lists... Done
W: Duplicate sources.list entry http://archive.canonical.com/ubuntu/ precise/partner i386 Packages (/var/lib/apt/lists/archive.canonical.com_ubuntu_dists_precise_partner _binary-i386_Packages)
W: Duplicate sources.list entry http://deb.opera.com/opera/ stable/non-free i386 Packages (/var/lib/apt/lists/deb.opera.com_opera_dists_stable_non-free_binary-i386_Packages)
W: You may want to run apt-get update to correct these problems


However, there is no duplicates!?

P.S. Of course, when i comment them error disappears

[steeldriver]

Do you have additional source files in the /etc/apt/sources.list.d/ directory maybe?