Schaefer, Timo H, author
Cambridge University Press, 2017
eBooks
Vaillant, George C., author
Penguin Books, 1950
Buku Teks
United Nations Educational, Scientific and Cultural Organization, 1977
Buku Teks
Diggins, John Patrick
W.W Norton, 1992
Buku Teks
Jarman, T.L., author
The Cresset Press, 1955
Buku Teks