$ apt-cache policy libical1 libical1a
libical1:
Installed: 1.0-1.2
Candidate: 1.0-1.2
Version table:
*** 1.0-1.2 0
100 /var/lib/dpkg/status
libical1a:
Installed: (none)
Candidate: 1.0-1.3
Version table:
1.0-1.3 0
500 http://http.debian.net/debian/ unstable/main amd64 Packages