Helpman, E. (1998). Explaining the structure of foreign trade: Where do we stand? Institut für Weltwirtschaft an der Universität.
Citazione stile Chigago Style (17a edizione)Helpman, Elhanan. Explaining the Structure of Foreign Trade: Where Do We Stand? Kiel: Institut für Weltwirtschaft an der Universität, 1998.
Citatione MLA (9a ed.)Helpman, Elhanan. Explaining the Structure of Foreign Trade: Where Do We Stand? Institut für Weltwirtschaft an der Universität, 1998.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.