docs: private List<Element> getTopicrefs(final Element root) {
          final List<Element> res = new ArrayList<>();
          final NodeList all = root.getElementsByTagName("*");
          for (int i = 0; i < all.getLength(); i++) {
              final Element elem = (Element) all.item(i);
              if (MAP_TOPICREF.matches(elem)
                      && isDitaFormat(elem.getAttributeNode(ATTRIBUTE_NAME_FORMAT))
                      && !elem.getAttribute(ATTRIBUTE_NAME_SCOPE).equals(ATTR_SCOPE_VALUE_EXTERNAL)) {
                  res.add(elem);
              }
          }
          return res;
      }