function showHide(layer_ref)
{
    if(layer_ref.length < 1)
        return;

    if(document.getElementById(layer_ref).style.display == "none")
        document.getElementById(layer_ref).style.display = "block";
    else
        document.getElementById(layer_ref).style.display = "none";
}

function additionalRelated()
{
    showHide('extra_related');
    showHide('hide_extra_related');
    showHide('show_extra_related');
}