private function referenceFieldsByTag()
    {
        $tag = $this->spec['field']['tag'];

        if ($this->cache->offsetExists($tag)) {
            return $this->cache[$tag];
        }

        if ('LDR' !== $tag) {
            $_fieldRef = $this->record->getFields($tag, true);
        } else {
            // tag = LDR
            $_fieldRef[] = $this->record->getLeader();
        }

        $this->cache[$tag] = $_fieldRef;

        return $_fieldRef;
    }