Cita APA

Black, C. E., & Helmreich, E. C. (1972). Twentieth century Europe: A history (Fourth edition.). New York: Alfred A.Knopf.

Citación estilo Chicago

Black, C. E.,, y E. C. Helmreich. Twentieth Century Europe: A History. Fourth edition. New York: Alfred A.Knopf, 1972.

Cita MLA

Black, C. E.,, y E. C. Helmreich. Twentieth Century Europe: A History. Fourth edition. New York: Alfred A.Knopf, 1972.