{HEAD ~ A relatively new extension} of the class library concept is to have {TAIL ~ a framework} of class libraries 
is to have
{ HEAD ~ A relatively new extension } of the class library concept is to have { TAIL ~ a framework } of class libraries
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH