*  @param b another list of pages
     *  @return a intersect b (as String[])
     *  @since 0.04
     */
    public static String[] intersection(String[] a, String[] b)
    {
        // @revised 0.11 to take advantage of Collection.retainAll()
        // @revised 0.14 genericised to all page titles, not just category members

        ArrayList<String> aa = new ArrayList<String>(5000); // silly workaroiund
        aa.addAll(Arrays.asList(a));
        aa.retainAll(Arrays.asList(b));
        return aa.toArray(new String[aa.size()]);
    }