function show_frank () {
  if (document.getElementById)
    document.getElementById("frank").style.visibility = "visible";
  if (document.getElementById)
    document.getElementById("foto_frank").style.visibility = "hidden";

}

function show_baerbel () {
  if (document.getElementById)
    document.getElementById("baerbel").style.visibility = "visible";
  if (document.getElementById)
    document.getElementById("foto_baerbel").style.visibility = "hidden";

}

function show_chris () {
  if (document.getElementById)
    document.getElementById("chris").style.visibility = "visible";
  if (document.getElementById)
    document.getElementById("foto_chris").style.visibility = "hidden";

}

function show_mstein () {
  if (document.getElementById)
    document.getElementById("mstein").style.visibility = "visible";
  if (document.getElementById)
    document.getElementById("foto_chris").style.visibility = "hidden";

}

function show_montag () {
  hide_dienstag(); hide_mittwoch(); hide_donnerstag(); hide_freitag(); hide_samstag();
  if (document.getElementById)
    document.getElementById("montag").style.visibility = "visible";
}

function hide_montag () {
  if (document.getElementById)
    document.getElementById("montag").style.visibility = "hidden";
}

function show_dienstag () {
  hide_montag(); hide_mittwoch(); hide_donnerstag(); hide_freitag(); hide_samstag();
  if (document.getElementById)
    document.getElementById("dienstag").style.visibility = "visible";
}

function hide_dienstag () {
  if (document.getElementById)
    document.getElementById("dienstag").style.visibility = "hidden";
}

function show_mittwoch () {
  hide_dienstag(); hide_montag(); hide_donnerstag(); hide_freitag(); hide_samstag();
  if (document.getElementById)
    document.getElementById("mittwoch").style.visibility = "visible";
}

function hide_mittwoch () {
  if (document.getElementById)
    document.getElementById("mittwoch").style.visibility = "hidden";
}

function show_donnerstag () {
  hide_dienstag(); hide_mittwoch(); hide_montag(); hide_freitag(); hide_samstag();
  if (document.getElementById)
    document.getElementById("donnerstag").style.visibility = "visible";
}

function hide_donnerstag () {
  if (document.getElementById)
    document.getElementById("donnerstag").style.visibility = "hidden";
}

function show_freitag () {
  hide_dienstag(); hide_mittwoch(); hide_donnerstag(); hide_montag(); hide_samstag();
  if (document.getElementById)
    document.getElementById("freitag").style.visibility = "visible";
}

function hide_freitag () {
  if (document.getElementById)
    document.getElementById("freitag").style.visibility = "hidden";
}

function show_samstag () {
  hide_dienstag(); hide_mittwoch(); hide_donnerstag(); hide_freitag(); hide_montag();
  if (document.getElementById)
    document.getElementById("samstag").style.visibility = "visible";
}

function hide_samstag () {
  if (document.getElementById)
    document.getElementById("samstag").style.visibility = "hidden";
}