protected function bootstrapNavs(array $items, $class, $stacked) {

        $attributes = [];

        $attributes["class"][] = "nav";
        $attributes["class"][] = $class;
        $attributes["class"][] = true === $stacked ? "nav-stacked" : null;

        $innerHTML = [];
        foreach ($items as $current) {
            $innerHTML[] = $this->bootstrapNav($current);
        }

        return static::coreHTMLElement("ul", "\n" . implode("\n", $innerHTML) . "\n", $attributes);
    }