Artikel Jurnal
Arntz, Helmut, author
The Press and Information Office of the federal Germa Govermant, [1967]
Buku Teks
Kitchen, Martin, author
Blackwell Pub, 2012
Buku Teks
Conant, James B., author
Harvard University Press, 1958
Buku Teks
Barraclough, Geoffrey, 1908-1984, author
Basil Blackwell, 1952
Buku Teks