Birdsall, S. S. (1992). American Geography. John Wiley and Sons.
Cita Chicago (17th ed.)Birdsall, Stephen S. American Geography. John Wiley and Sons, 1992.
Cita MLA (9th ed.)Birdsall, Stephen S. American Geography. John Wiley and Sons, 1992.
Atenció: Aquestes cites poden no estar 100% correctes.