function howFound() {
    var hf = document.getElementById('howfound').value;

    if ((hf == "2") || (hf == "4") || (hf == "17") || (hf == "18")) {
	document.getElementById('hfothdv').style.display='block';
    } else {
	document.getElementById('hfothdv').style.display='none';
    }
}