Read through at least twice<b>,</b> and thereupon<b>,</b> until no additional mistakes are found. <br/><br/>or<br/><br/>Read through at least twice<b>,</b> and<b>,</b> thereupon<b>,</b> until no additional mistakes are found. <br/><br/>Notice the commas. <br/><br/>If you believe neither of these is correct, tell me why.