Twentieth century Europe;
a history /
[by] C. E. Black [and] E. C. Helmreich.

APA Citation

Black, C. E. (Cyril Edwin)., Helmreich, E. Christian. (1966). Twentieth century Europe: a history. 3d ed. New York: Knopf.

MLA Citation

Black, Cyril E. (Cyril Edwin), 1915-1989, and Ernst Christian Helmreich. Twentieth Century Europe: a History. 3d ed. New York: Knopf, 1966.

Warning: These citations may not always be complete (especially for serials).