Missing packages in ros natty repository

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Hi, i'm trying to install ros in my ubuntu natty, running in a virtual box, but it appears that there is some missing packages. I Followed the steps in http://www.ros.org/wiki/diamondback/I... but when i try to install the package ros-diamondback-desktop-full it just doesn't show. I could only isntall the ros-diamondback-desktop.

Also, when i search for the gazebo stack, i can't find the diamondback one. Here is my output of the command "apt-cache search gazebo":

ros-diamondback-pr2-common - PR2 robot description and PR2-specific messages
ros-unstable-cob-simulation - Care-O-bot stack with simulation packages
ros-unstable-pr2-common - PR2 robot description and PR2-specific messages
ros-unstable-simulator-gazebo - Gazebo Simulator

i just have no idea why i can't find the packages i want to install u_u