{HEAD ~ Either a single ester} or a mixture of esters can be used as {TAIL ~ organic acid esters} 
used as
{ HEAD ~ Either a single ester } or a mixture of esters can be used as { TAIL ~ organic acid esters }
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL