Heck, H. J. (1953). Foreign commerce. McGraw-Hill.
Cita Chicago (17th ed.)Heck, Harold Joseph. Foreign Commerce. New York: McGraw-Hill, 1953.
Cita MLA (9th ed.)Heck, Harold Joseph. Foreign Commerce. McGraw-Hill, 1953.
Atenció: Aquestes cites poden no estar 100% correctes.