World Tourism Organization. (2002). Voluntary initiatives for sustainable tourism: Worldwide inventory and comparative analysis of 104 eco-labels, awards and self-commitments. World Tourism Organization.
Παραπομπή σε μορφή Chicago (17η εκδ.)World Tourism Organization. Voluntary Initiatives for Sustainable Tourism: Worldwide Inventory and Comparative Analysis of 104 Eco-labels, Awards and Self-commitments. Madrid: World Tourism Organization, 2002.
Παραπομπή σε μορφή MLA (9th εκδ.)World Tourism Organization. Voluntary Initiatives for Sustainable Tourism: Worldwide Inventory and Comparative Analysis of 104 Eco-labels, Awards and Self-commitments. World Tourism Organization, 2002.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.