https://download.owncloud.org/download/repositories/stable/owncloud/
xUbuntu_14.04 owncloud-9.0.1-3.1
You can add the repository key to apt. Keep in mind that the owner of the key may distribute updates, packages and repositories that your system will trust (more information). Run the following shell commands as root to trust the repository:
wget -nv https://download.owncloud.org/download/repositories/stable/xUbuntu_14.04/Release.key...