{HEAD ~ Method} and system for incrementally selecting and providing {TAIL ~ relevant search engines} in response to a user query 
for incrementally selecting
{ HEAD ~ Method } and system for incrementally selecting and providing { TAIL ~ relevant search engines } in response to a user query
HEAD HEAD HEAD HEAD HEAD OTH OTH REL REL REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH