Dear all,
the group was configured to accept posts from members only since its
creation, but unfortunately it seems now that this is not enough
anymore. Recent spam-bots are quite smart and they subscribe to the
group before to send all their spam messages. The only way to prevent
this is to remove them by hand and to allow subscription on new
members only after approval by moderators.
These two actions have been taken now, let see if they will work, or
we will be forced to close the group.

Cordially,
Carlo, ICTP