Comment 144 for bug 1167114

@Nathaniel

proposed is only for advanced users:
https://wiki.ubuntu.com/Testing/EnableProposed

OR

cd /etc/apt/sources.list.d/
sudo echo -n 'deb http://archive.ubuntu.com/ubuntu/ ' > proposed.list
sudo echo -n 'quantal-proposed main restricted ' >> proposed.list
sudo echo 'universe multiverse' >> proposed.list

sudo apt-get update
sudo apt-get install linux-headers-3.5.0-28 linux-headers-3.5.0-28-generic linux-image-3.5.0-28-generic linux-image-extra-3.5.0-28-generic
sudo rm /etc/apt/sources.list.d/ubuntu-proposed.list

Last command is to remove proposed repo.