function emailFriend()
{
mail_str = "mailto:?subject=AHP:  " + document.title;
mail_str += "&body=A colleague has sent you a link to '" + document.title + "' on AHP.org.  ";
mail_str += "You can view it by clicking on the following link:  " + location.href; 
location.href = mail_str;
}

function isValidCreditCard(type, ccnum) {

	    validLength = true;
	    if (type == "Visa") {
	        if (ccnum.length != 16) { validLength = false }
	        // Visa: length 16, prefix 4
	        var re = /^4\d{3}-?\d{4}-?\d{4}-?\d{4}$/;
	    } if (type == "MasterCard") {
	        if (ccnum.length != 16) { validLength = false }
	        // Mastercard: length 16, prefix 51-55
	        var re = /^5[1-5]\d{2}-?\d{4}-?\d{4}-?\d{4}$/;
	    } if (type == "Amex") {
	        if (ccnum.length != 15) { validLength = false }
	        // American Express: length 15, prefix 34 or 37.
	        var re = /^3[4,7]\d{13}$/;
	    }
	    if (!validLength) return false;
	    if (!re.test(ccnum)) return false;
	    // Checksum ("Mod 10")
	    // Add even digits in even length strings or odd digits in odd length strings.
	    var checksum = 0;
	    for (var i = (2 - (ccnum.length % 2)); i <= ccnum.length; i += 2) {
	        checksum += parseInt(ccnum.charAt(i - 1));
	    }
	    // Analyze odd digits in even length strings or even digits in odd length strings.
	    for (var i = (ccnum.length % 2) + 1; i < ccnum.length; i += 2) {
	        var digit = parseInt(ccnum.charAt(i - 1)) * 2;
	        if (digit < 10) { checksum += digit; } else { checksum += (digit - 9); }
	    }
	    if ((checksum % 10) == 0) return true; else return false;
	}