public function filter_by_term($term) {
        $this->where[] = sprintf("(%s = :filterterma OR %s = :filtertermb)",
            self::resolve_field('concept', 'entries'),
            self::resolve_field('alias', 'alias'));
        $this->params['filterterma'] = $term;
        $this->params['filtertermb'] = $term;
    }