Frederick A. Praeger, 1966
Buku Teks
Rand McNally, [date of publication not identified]
Buku Referensi
Petrides, George A.
Houghton Mifflin, 1988
Buku Teks
Grolier Incorporated, 1964
Buku Referensi
edited by. Valters Nollendorfs and Geoffrey S. Koby
German Studies Information, 1991
Buku Referensi