APA

Hacker L. M., Zahler H. S., . (1952). The United States in the 20th century. New York: Appleton-Century-Crofts.

Chicago

Hacker Louis Morton, Zahler Helene Sara, . 1952. The United States in the 20th century. New York: Appleton-Century-Crofts.

Harvard

Hacker L. M., Zahler H. S., . (1952). The United States in the 20th century. New York: Appleton-Century-Crofts.

MLA

Hacker Louis Morton, Zahler Helene Sara, . The United States in the 20th century. New York: Appleton-Century-Crofts. 1952.