Loomis, Charles P.
Prentice-Hall, 1957
Buku Teks
edited by Howard Newby
John Wiley & Sons, 1978
Buku Teks
Chitambar, J. B.
Wiley Eastern Limited, 1973
Buku Teks
Smith, T. Lynn
FA Davis, 1970
Buku Teks
Long, Norman
Tavistock Publication, 1980
Buku Teks