code: private void addNthChild(final boolean byType) {
  		for (Node node : nodes) {
  			Index index = helper.getIndexInParent(node, byType);
  
  			if (specifier.isMatch(index.index+1))
  				result.add(node);
  		}
  	}
docs: Add the {@code :nth-child} elements.
  
  @see <a href="http://www.w3.org/TR/css3-selectors/#nth-child-pseudo"><code>:nth-child</code> pseudo-class</a>