Weber, Max, 1864-1920, author
Macmillan, 1964
Buku Teks
Wheare, K. C.
Oxford University Press, 1963
Buku Teks
Library of Congress, Cataloging Distribution Service, 1997
Buku Referensi
Milkha S. Aulakh, Cynthia A. Grant, editor
CRC Press, 2008
Buku Teks
Fordham, R.
Collins, 1985
Buku Teks