E: Package 'openssh-client' существуешь не installation candidate

How to install openssh cilent and server on ubundu 13.04. i tried я отдаю apt-get install openssh-client on 13.04, but i got this ошибка. i could not install it.

mphil@mphil:~$ sudo apt-get install openssh-client
[sudo] password for mphil: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package openssh-client is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'openssh-client' has no installation candidate