APA

Ferm V., . (1950). A history of philosophical systems. New York: Philosophical Library.

Chicago

Ferm Vergilius, . 1950. A history of philosophical systems. New York: Philosophical Library.

Harvard

Ferm V., . (1950). A history of philosophical systems. New York: Philosophical Library.

MLA

Ferm Vergilius, . A history of philosophical systems. New York: Philosophical Library. 1950.