List of mirrors:
 * [mirror1]: http://mirror.yandex.ru/debian/ stretch
 * [mirror2]: http://mirror.yandex.ru/debian/ stretch [src]
 * [mirror3]: http://mirror.yandex.ru/debian/ stretch
 * [mirror4]: http://download.opensuse.org/repositories/Apache:/MirrorBrain/Debian_9.0/ ./

To get more information about mirror, run `aptly mirror show <name>`.