apt-cache policy btrfs-tools
btrfs-tools:
  Installed: 0.19+20100601-3ubuntu3
  Candidate: 0.19+20100601-3ubuntu3
  Version table:
 *** 0.19+20100601-3ubuntu3 0
        500 http://archive.ubuntu.com/ubuntu/ precise/main amd64 Packages
        100 /var/lib/dpkg/status