function toggle(id) {
	ul = "ul_" + id;
	img = "img_" + id;
	ulElement = document.getElementById(ul);
	imgElement = document.getElementById(img);
	if (ulElement) {
		if (ulElement.className == 'closed') {
			ulElement.className = "open";
			imgElement.src = "images/minus.png";
		} else {
			ulElement.className = "closed";
			imgElement.src = "images/plus.png";
		}
	}
}