Nevid, Jeffrey S., author
Prentice-Hall, 1997
Buku Teks
United Nations Departemen of Public Information, 1990
Buku Teks
Brown, A.J., author
George Allen and Unwin, 1959
Buku Teks
Brown, A.J., author
George Allen and Unwin, 1959
Buku Klasik
Perkins, J.O.N., author
Sun Books, 1968
Buku Teks