{HEAD ~ The surfaces} of oxidation films 13a, 13b are {TAIL ~ mirror} finished if necessary 
are
{ HEAD ~ The surfaces } of oxidation films 13a , 13b are { TAIL ~ mirror } finished if necessary
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH