Carl Duisberg-Gesellsechft
Bonn Ferd, Dummlers Verlag
Buku Referensi
Amadeo, Santos P.
Columbia University Press, 1943
Buku Teks
Foreign office of the federal Republic of Germany , 1982
Buku Teks
Walichnowski, Tadeusz
Interpress Punlisher , 1968
Buku Teks
Chamberlain, Joseph P.
Books for Libraries Press , 1942
Buku Teks