{TAIL ~ First coal solvation} involves {HEAD ~ formation} of free radicals which are stabilized by hydrogen 
{ TAIL ~ First coal solvation } involves { HEAD ~ formation } of free radicals which are stabilized by hydrogen
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH