O`Brien, Robert W.
Houghton Mifflin, 1964
Buku Teks
Broom, Leonard
Harper, 1981
Buku Teks
Smith, Charles W.
Basil Blackwell, 1979
Buku Teks
Currier, Glenn
Harcourt, college Pub., 1997
Buku Teks
Collins, Randall, author
Oxford University Press , 1992
Buku Teks