function rewrite_external (do_blank, add_image)
{
	var main = document.getElementById("mainContent");
	var a = main.getElementsByTagName("a");
	var i;
	var ai;
	var pattern1 = /^http/;
	var pattern2 = /si\.edu/;
	var href;
	var rel;
 
	for (i = 0; i < a.length; i++) {
		ai = a[i];
		href = ai.getAttribute("href");
		rel = ai.getAttribute("rel");
		if ((pattern1.test(href) && !pattern2.test(href)) || rel == "external") {
			if (do_blank) ai.target = "_blank";
			if (add_image) ai.innerHTML += '<img src="_img/external_link.gif" alt="[External Link]" />';
		}
	}
}