Congress of the Association Internationale d' Experts Scientifiques du Tourisme Bulgary. (1979). Manpower in tourism: Proceedings of the 29th Congress of the Association Internationale d' Experts Scientifiques du Tourisme , Droujba pres de Varna (Bulgarie), 2-8 September 1979. AIEST.
Chicago (17e ed.) BronvermeldingCongress of the Association Internationale d' Experts Scientifiques du Tourisme Bulgary. Manpower in Tourism: Proceedings of the 29th Congress of the Association Internationale D' Experts Scientifiques Du Tourisme , Droujba Pres De Varna (Bulgarie), 2-8 September 1979. Berne, Switzerland: AIEST, 1979.
MLA (9e ed.) BronvermeldingCongress of the Association Internationale d' Experts Scientifiques du Tourisme Bulgary. Manpower in Tourism: Proceedings of the 29th Congress of the Association Internationale D' Experts Scientifiques Du Tourisme , Droujba Pres De Varna (Bulgarie), 2-8 September 1979. AIEST, 1979.