Jessup, Ronald
Macdonald, 1968
Buku Teks SO
Priestley, John Boynton, 1894-1984
Garden City Books, 1959
Buku Teks SO
Christian Baumgartner , Martin Uitz, Karl Krainer, Peter Hasslacher
The Federal Press Service, 2002
Buku Referensi
Ames, Louise Bates
Delta book, 1976
Buku Teks
Moore, Raylyn
Bowling Green : Bowling Green University Popular, 1974
Buku Teks