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