*/
  public static <K extends Comparable<? super K>, V> ImmutableSortedMap<K, V> of(
      K k1, V v1, K k2, V v2, K k3, V v3, K k4, V v4) {
    return fromEntries(entryOf(k1, v1), entryOf(k2, v2), entryOf(k3, v3), entryOf(k4, v4));
  }

  /**
   * Returns an immutable sorted map containing the given entries, sorted by the natural ordering of
   * their keys.
   *