Robert Maynard Hutchins, editor in chief
Encyclopaedia Britannica, Inc., 1952
Buku Referensi
Mortimer J. Adler, editor in chief
Encyclopedia Britanica, 1994
Buku Referensi
Holt, Rinehart and Winston, 1961
Buku Teks
Artikel Jurnal
edited by Harold C. Gardiner
Devin-Adair Co., 1949
Buku Teks