Hodgkinson, Harold L.
McGraw-Hill , 1971
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
Smith, Huston, author
Harper & Brothers, 1955
Buku Teks