{HEAD ~ The Ra} and Ra may preferably provide {TAIL ~ Ra/Ra ratio} of at most 0.8 
preferably provide
{ HEAD ~ The Ra } and Ra may preferably provide { TAIL ~ Ra / Ra ratio } of at most 0.8
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH