Ashby, Eric
Stanford University Press, 1978
Buku Teks
Knapp, Brian J., author
Longman, 1992
Buku Teks
Jackson, Andrew R.W., author
Longman, 1996
Buku Teks
Meyer, Evelyn E.
World Health Organization, 1975
Buku Teks
edited by Moryteza Honari and Thomas Boleyn
Routledge, 1999
Buku Teks