(1961). International travel statistics =: Statistiques du tourisme international = Estadisticas del turismo international (25th ed.). Geneve: International Union of Official Travel Organisations.
Παραπομπή Chicago StyleInternational Travel Statistics =: Statistiques Du Tourisme International = Estadisticas Del Turismo International. 25th ed. Geneve: International Union of Official Travel Organisations, 1961.
Παραπομπή MLAInternational Travel Statistics =: Statistiques Du Tourisme International = Estadisticas Del Turismo International. 25th ed. Geneve: International Union of Official Travel Organisations, 1961.
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