function radioButton (myObj) {
	//color
	var buttonsColl = document.getElementById("chapter-menu").getElementsByTagName("TD");
	
	for (i = 0; i < buttonsColl.length; i++) {
		buttonsColl[i].className = "chapter-menu-cell";
		buttonsColl[i].style.backgroundColor = "#2D4747";
	}
	myObj.className = "chapter-menu-cell-on";
	myObj.style.backgroundColor = "#3F6363";
	
	//open-close
	var divName = myObj.id
	var chaptersColl = document.getElementById("chapter-window").getElementsByTagName("DIV");
	
	divName = divName.substring(0, divName.length-5);
	for (i = 0; i < chaptersColl.length; i++) {
		if (chaptersColl[i].id == divName) {
			chaptersColl[i].style.display = "block"
		} else {
			chaptersColl[i].style.display = "none"
		}
	}
}