Cita APA (7th ed.)

Ridge, M., & Billington, R. A. (1980). America's frontier story: A documentary history of westward expansion. R. E. Krieger Pub. Co..

Cita Chicago (17th ed.)

Ridge, Martin, i Ray Allen Billington. America's Frontier Story: A Documentary History of Westward Expansion. Huntington, N.Y: R. E. Krieger Pub. Co., 1980.

Cita MLA (8th ed.)

Ridge, Martin, i Ray Allen Billington. America's Frontier Story: A Documentary History of Westward Expansion. R. E. Krieger Pub. Co., 1980.