Example 4.2 has: > (Arica<sup>I</sup>, Santiago<sup>I</sup>)∈flight and flight ⊆ connectsTo<sup>I</sup>. There should be <sup>I</sup> after flight in both occurrences: > (Arica<sup>I</sup>, Santiago<sup>I</sup>)∈flight<sup>I</sup> and flight<sup>I</sup> ⊆ connectsTo<sup>I</sup>.