APT preferences et repos tiers

[debian@fantasymail.com]

Bonjour, je cherche à modifier mon fichier préférences pour y inclure
ces 2 repos tiers:

deb http://www.tvfreeplayer.com/linux/falcon debian mods
deb http://download.tuxfamily.org/shames/debian-sid/desktopfx/unstable/
./

Voici mon fichier preferences:

Package: *
Pin: release o=apt-build
Pin-Priority: 999

Package: *
Pin: release o=Debian,a=testing,l=Debian-Security
Pin-Priority: 998

Package: *
Pin: release o=Unofficial Multimedia Packages,a=testing,l=Unofficial
Multimedia Packages
Pin-Priority: 997

Package: *
Pin: release o=Debian,a=testing,l=Debian
Pin-Priority: 996

Package: *
Pin: release o=volatile.debian.org,a=stable,l=debian-volatile
Pin-Priority: 995

Package: *
Pin: release o=Debian,a=stable,l=Debian-Security
Pin-Priority: 994

Package: *
Pin: release o=Unofficial Multimedia Packages,a=stable,l=Unofficial
Multimedia Packages
Pin-Priority: 993

Package: *
Pin: release v=4.0r0,o=Debian,a=stable,l=Debian
Pin-Priority: 992

Package: *
Pin: release o=Unofficial Multimedia Packages,a=unstable,l=Unofficial
Multimedia Packages
Pin-Priority: 991

Package: *
Pin: release o=Debian,a=unstable,l=Debian
Pin-Priority: 990

Package: *
Pin: release o=Unofficial Multimedia
Packages,a=experimental,l=Unofficial Multimedia Packages
Pin-Priority: 989

Package: *
Pin: release o=Debian,a=experimental,l=Debian
Pin-Priority: 988

D'apres man apt_preferences je comprend que je dois fixer un
Pin-Priority supérieur à 1000 pour ces 2 repos. Mais dans ces 2 cas je
n'ai pas de répertoire /dists/dist-name, donc comment puis-je fixé le
paramètre a= ?

Merci.