{TAIL ~ A distributed index} may be used to implement an instant messaging system in {HEAD ~ a group} of participating peers 
{ TAIL ~ A distributed index } may be used to implement an instant messaging system in { HEAD ~ a group } of participating peers
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH