1 ) ? $current_page - 1 : 0;
$next_page = $current_page + 1;
$licenses = get_catalog_licenses();
$available_licenses = get_available_licenses( $catalog_data );
$institutions = get_institutions();
$available_institutions = get_available_institutions( $catalog_data );
$subjects = ( defined( 'PB_PLUGIN_VERSION' ) ) ? \Pressbooks\Metadata\get_thema_subjects() : [];
$available_subjects = get_available_subjects( $catalog_data );
if ( ! empty( $catalog_data['books'] ) ) :
get_header(); ?>
set_404();
status_header( 404 );
get_header();
?>