Cita APA (7a ed.)
Schopenhauer, A. The Fourfold Root of the Principle of Sufficient Reason. Open Court.
Cita estilo Chicago (17a ed.)
Schopenhauer, Arthur. The Fourfold Root of the Principle of Sufficient Reason. La Salle, EUA: Open Court.
Cita MLA (9a ed.)
Schopenhauer, Arthur. The Fourfold Root of the Principle of Sufficient Reason. Open Court.
警告：這些引文格式不一定是100％准確.