MLA

Sletterdahl, Peter John. The Nightshirt in Politics / by P. J. "Twilight" Orn [i. e. P. J. Sletterdahl]. Ajax Pub. Co., 1926. https://collections.library.yale.edu/catalog/10701751.

APA, 6th edition

Sletterdahl, P. J. (1926). The nightshirt in politics / by P. J. "Twilight" Orn [i. e. P. J. Sletterdahl]. [Book covers, Covers (Illustrations), Historiography]. Ajax Pub. Co., https://collections.library.yale.edu/catalog/10701751.