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