The color formers and color developers combine upon exposure to an imaging force, such as heat or pressure, to form {HEAD ~ different colored visible areas} on {TAIL ~ the sheet} 
The color formers and color developers combine upon exposure to an imaging force , such as heat or pressure , to form { HEAD ~ different colored visible areas } on { TAIL ~ the sheet }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL