var imageFiles_z_13 = new Array();
imageFiles_z_13['0'] = new Array ('_images/z_ENVIRONMENTAL_FACTS.gif', '_images/z_ENVIRONMENTAL_FACTSMouseover.gif');

function image_on_z_13 (position) {
   var doc = eval("document.imagez_13" + position);
   doc.src = imageFiles_z_13[position][1];
}

function image_off_z_13 (position) {
   var doc = eval("document.imagez_13" + position);
   doc.src = imageFiles_z_13[position][0];
}