{HEAD ~ The method} 1 including collecting {TAIL ~ gas molecules} containing the other of said isotopes traveling along said other path 
including collecting
{ HEAD ~ The method } 1 including collecting { TAIL ~ gas molecules } containing the other of said isotopes traveling along said other path
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH