Preferably, {HEAD ~ hydrogen} is introduced into {TAIL ~ the coal bed} in an amount within the range of 0.2–1.0 standard cubic feet of hydrogen for each standard cubic foot of methane recovered from the coal bed formation 
is introduced into
Preferably , { HEAD ~ hydrogen } is introduced into { TAIL ~ the coal bed } in an amount within the range of 0.2–1.0 standard cubic feet of hydrogen for each standard cubic foot of methane recovered from the coal bed formation
OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH