Sorensen, H. (1995). International air fares: Construction and ticketing. South-Western Pub.
Citazione stile Chigago Style (17a edizione)Sorensen, Helle. International Air Fares: Construction and Ticketing. Cincinnati, Ohio: South-Western Pub, 1995.
Citatione MLA (9a ed.)Sorensen, Helle. International Air Fares: Construction and Ticketing. South-Western Pub, 1995.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.