Antezana, Fernando
World Health Organization, 1996
Buku Teks
Wonderling, David, author
Open University Press, 2005
Buku Teks
Phelps, Charles E., author
Harper Collins, 1992
Buku Teks
Ashmore, Malcolm
Open University Press, 1990
Buku Teks
Donaldson, Cam, author
Macmillan, 1994
Buku Teks