function shBase(course){
								var el, tmp_el
								if (!(el = document.getElementById('base' + course))) return false
								for (i=2; i <4; i++){
									if (!(tmp_el = document.getElementById('base' + i))) 
										break
									if ((tmp_el.className.search('detailed') == -1)&&(tmp_el.id == el.id)){
										tmp_el.className = tmp_el.className.replace(/hidden/, 'detailed');
									}
									else{
										tmp_el.className = el.className.replace(/detailed/, 'hidden')
									}
								}
							}