MLA

Gilbert, Katharine, and Hellmut Kühn. A History of Esthetics. London: Thames and hudson, 1956.

APA

Gilbert, K., & Kühn, H. (1956). A History of Esthetics. London: Thames and hudson.

Chicago

Gilbert, Katharine, and Hellmut Kühn. A History of Esthetics. London: Thames and hudson, 1956.