Spencer, H. (1891). The Principles of Ethics (2nd thousand.). Williams and Norgate.
Chicago-Zitierstil (17. Ausg.)Spencer, Herbert. The Principles of Ethics. 2nd thousand. London ; Edinburgh: Williams and Norgate, 1891.
MLA-Zitierstil (8. Ausg.)Spencer, Herbert. The Principles of Ethics. 2nd thousand. Williams and Norgate, 1891.
警告：这些引文格式不一定是100％准确.