private void appendCallersList(RefElement element, @NotNull StringBuilder buf, Set<? super RefElement> mentionedElements, boolean appendCallees){
    final Set<RefElement> possibleChildren = getPossibleChildren(element);
    if (!possibleChildren.isEmpty()) {
      if (appendCallees){
        appendHeading(buf, JavaBundle.message("inspection.export.results.callees"));
      }
      final @NonNls String ul = "<ul>";
      buf.append(ul);
      for (RefElement refElement : possibleChildren) {
        if (!mentionedElements.contains(refElement)) {
          mentionedElements.add(refElement);
          final @NonNls String li = "<li>";
          buf.append(li);
          appendElementReference(buf, refElement, true);
          final @NonNls String closeLi = "</li>";
          buf.append(closeLi);
          appendCallersList(refElement, buf, mentionedElements, false);
        }
      }
      final @NonNls String closeUl = "</ul>";
      buf.append(closeUl);
    }
  }
private void appendCallersList(RefElement element, @NotNull StringBuilder buf, Set<? super RefElement> mentionedElements, boolean appendCallees)