The server then receives, from a client, a request for an advertisement to display to the first user, selects one of {HEAD ~ the other users} having {TAIL ~ a friend} rank satisfying a predetermined threshold, and transmits, to the client, an advertisement portraying the selected additional user 
having
The server then receives , from a client , a request for an advertisement to display to the first user , selects one of { HEAD ~ the other users } having { TAIL ~ a friend } rank satisfying a predetermined threshold , and transmits , to the client , an advertisement portraying the selected additional user
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH