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Travel and tourism. An introd. to travel agency operations
Lehmann, Armin Dieter, (1978)
The tourism sector in the Community : a study of concentration, competition and competitiveness
Casini, S., (1985)
The Travel Industry
Gee, Chuck Y., (1984)
Die Reise-Gesellschaft : Deutschlands Urlauber und die Tourismus-Industrie
Bensmann, Hans, (1976)