+ deb-src http://cdn.debian.net/debian/ stable main contrib non-free
+
+# security updates:
+ deb http://security.debian.org/ stable/updates main contrib
+ deb-src http://security.debian.org/ stable/updates main contrib
+
+# backports:
+ deb http://backports.debian.org/debian-backports squeeze-backports main
+ deb-src http://backports.debian.org/debian-backports squeeze-backports main