{HEAD ~ a scanner} which detects {TAIL ~ a side} of a sheet on which an image is formed using a thermally decolorable coloring agent 
{ HEAD ~ a scanner } which detects { TAIL ~ a side } of a sheet on which an image is formed using a thermally decolorable coloring agent
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH