var radioStatus = new Object();
function check(obj) {
	if (radioStatus[obj.name]==null) { 
		radioStatus[obj.name] = obj.value;
		}
	else {
		if (radioStatus[obj.name] == obj.value) {
			obj.checked = false;
			radioStatus[obj.name] = null;
			}
		else {
			radioStatus[obj.name] = obj.value;
			}
		}
	}
function availextra(foo)
{
if (foo=='p') {document.getElementById('availextra').innerHTML='';document.getElementById('availextra2').innerHTML='';}
else {
if (foo=='') {document.getElementById('availextra').innerHTML='';document.getElementById('availextra2').innerHTML='';}
else {document.getElementById('availextra').innerHTML='<input name="reference" style="text" size=60 maxlength=255>';}
}
if (foo=='o') {document.getElementById('availextra2').innerHTML='(URL)';}
if (foo=='u') {document.getElementById('availextra2').innerHTML='(citation)';}
if (foo=='r') {document.getElementById('availextra2').innerHTML='(repository name and location, location of tree)';}
}