var chronoNo  = new Image(); chronoNo.src  = 'images/nav_1ch.gif';
var chronoYes = new Image(); chronoYes.src = 'images/nav_1ch_s.gif';
var biblioNo  = new Image(); biblioNo.src  = 'images/nav_2bi.gif';
var biblioYes = new Image(); biblioYes.src = 'images/nav_2bi_s.gif';
var photoNo  = new Image(); photoNo.src  = 'images/nav_3ph.gif';
var photoYes = new Image(); photoYes.src = 'images/nav_3ph_s.gif';
var eventsNo  = new Image(); eventsNo.src  = 'images/nav_4ev.gif';
var eventsYes = new Image(); eventsYes.src = 'images/nav_4ev_s.gif';
var excerptsNo  = new Image(); excerptsNo.src  = 'images/nav_5ex.gif';
var excerptsYes = new Image(); excerptsYes.src = 'images/nav_5ex_s.gif';
var booksNo  = new Image(); booksNo.src  = 'images/nav_6bo.gif';
var booksYes = new Image(); booksYes.src = 'images/nav_6bo_s.gif';

function over(which) {
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}
function out(which) {
  document.images[which].src = "images/nav_"+which+".gif";
}