code: private void addAdjacentSiblingElements() {
          for (Node node : nodes) {
              Node n = DOMHelper.getNextSiblingElement(node);
              if (n != null) {
                  String tag = selector.getTagName();
                  if (tagEquals(tag, DOMHelper.getNodeName(n)) || tag.equals(Selector.UNIVERSAL_TAG)) {
                      result.add(n);
                  }
              }
          }
      }
docs: Add adjacent sibling elements.
  
  @see <a href="http://www.w3.org/TR/css3-selectors/#adjacent-sibling-combinators">Adjacent sibling combinator</a>