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