Παραπομπή APA
World Tourism Organization. (1999). Seminar on frontier statistics in European countries (Surveys on inbound & outbound tourism), WTO Headquarters, Madrid, 17 - 18th March 1998. Madrid, Spain: World Tourism Organization.
Παραπομπή Chicago StyleWorld Tourism Organization. Seminar On Frontier Statistics in European Countries (Surveys On Inbound & Outbound Tourism), WTO Headquarters, Madrid, 17 - 18th March 1998. Madrid, Spain: World Tourism Organization, 1999.
Παραπομπή MLAWorld Tourism Organization. Seminar On Frontier Statistics in European Countries (Surveys On Inbound & Outbound Tourism), WTO Headquarters, Madrid, 17 - 18th March 1998. Madrid, Spain: World Tourism Organization, 1999.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.