Fodor's Cruises and Ports of call / Daniel and Sally Grotta
Cruzeiros no Rio Douro / EnDouro Turismo, S.A.
The world cruise ship industry in the 1990s / Tony Peisley
Prospective touristique et marchés porteurs
The japanese overseas travel market in the 1990s / by Stephen Morris
Cruzeiros no rio Douro / Endouro Turismo
The business of tourism / J. Christopher Holloway
The total traveler by ship : a complete guide to sea travel / Ethel Blum
Quintas do Douro : Turismo no Espaço Rural
Tourisme et intégration européenne / CIACO