The encyclopedia of philosophy volume 7 and 8
Paul Edwards, editor in chief
Macmilan , 1972
Buku Referensi
International encyclopedia of the social sciences : volume 7 & 8
edited by David L. Sills
Macmillan and The Free Press, 1968
Buku Referensi
Encyclopedia of knowledge : volume 7
Grolier Incorporated, 1991
Buku Referensi
The Encyclopedia Americana : volume 7
Grolier, 1994
Buku Referensi
The Encyclopedia Americana : volume 7
Americana Corporation, 1977
Buku Referensi