Cita APA (7a ed.)

Freeman, R. A. (1936). The Penrose mystery. Blue Ribbon Books.

Cita Chicago Style (17a ed.)

Freeman, R. Austin. The Penrose Mystery. New York: Blue Ribbon Books, 1936.

Cita MLA (8a ed.)

Freeman, R. Austin. The Penrose Mystery. Blue Ribbon Books, 1936.