{HEAD ~ The gas} used in the present invention should contain {TAIL ~ at least about 70 mol percent hydrogen} 
contain
{ HEAD ~ The gas } used in the present invention should contain { TAIL ~ at least about 70 mol percent hydrogen }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL