{HEAD ~ Recovery} of methane from the coal beds can also be facilitated by {TAIL ~ the injection} into the formation of an inert stripping gas such as nitrogen 
facilitated by
{ HEAD ~ Recovery } of methane from the coal beds can also be facilitated by { TAIL ~ the injection } into the formation of an inert stripping gas such as nitrogen
HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH