"web.MIT.edu",
          "www.google.com",
          "www.state.pa.us",
          "www4.yahoo.co.uk"
          // keep-sorted end
          );

  private static final ImmutableSet<String> NON_RS =
      ImmutableSet.<String>builder().addAll(NON_PS).addAll(PS_NOT_RS).build();

  private static final ImmutableSet<String> TOP_UNDER_REGISTRY_SUFFIX =
      ImmutableSet.of("google.com", "foo.Co.uk", "foo.ca.us.");