Liu, Jeeloo, author
Wiley Blackwell, 2018
Buku Teks
Raz, Joseph, author
Oxford Univesity Press, 2009
Buku Teks
Raz, Joseph, author
Clarendon Press, 1979
Buku Teks
Irvan Syah, author
Fakultas Ilmu Pengetahuan dan Budaya Universitas Indonesia, 2011
UI - Skripsi (Open)
Robert Maynard Hutchins, editor in chief
Encyclopaedia Britannica, Inc., 1952
Buku Referensi