Sidgwick, H., & Widgery, A. G. (1949). Outlines of the history of ethics: For English readers / by Henry Sidgwick. With an additional chapter by Alban G. Widgery. Macmillan.

Sidgwick, Henry, and Alban G. Widgery. Outlines of the History of Ethics: For English Readers / by Henry Sidgwick. With an Additional Chapter by Alban G. Widgery. London: Macmillan, 1949.

Sidgwick, Henry, and Alban G. Widgery. Outlines of the History of Ethics: For English Readers / by Henry Sidgwick. With an Additional Chapter by Alban G. Widgery. Macmillan, 1949.