Copyright for network-manager-strongswan source package in Bionic

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Upstream-Name: NetworkManager-strongswan
Upstream-Contact: Martin Willi 
Source: https://download.strongswan.org/NetworkManager

Files: *
Copyright: 2008-2009, Martin Willi 
           2005-2008, Dan Williams
           2005, David Zeuthen
License: GPL-2

License: GPL-2
 On Debian systems the full text of the GNU General Public License can be found
 in the `/usr/share/common-licenses/GPL-2' file.