Department of Health , 1977
Buku Teks
Hallahan, Daniel P., author
Allyn and Bacon, 1994
Buku Teks
Hallahan, Daniel P., author
Prentice-Hall, 1988
Buku Teks
Noor, Abdun, author
World Bank, 1981
Buku Teks
Conant, James B., author
Oxford University Press, 1946
Buku Teks