Smith, Huston, author
Harper & Brothers, 1955
Buku Teks
UNESCO, 1978
Buku Teks
Her Majesty's Stationery Office, 1987
Buku Teks
edited by Maria Slowey, David Watson
Open University Press, 2003
Buku Teks
Mayhew, Lewis B., author
Jossey-Bass, 1973
Buku Teks