Hansen, Roger D.
McGraw-Hill Book, 1980
Buku Teks
Guile, Melanie
Heinemann Library, 2003
Buku Teks
Pan American Health Organization
PAHO, 1992
Buku Teks
edited by Amanda Gouws and Daiva Stasiulis
Routledge, 2014
Buku Teks
Lundestad, Geir
Norwegian University Press, 1986
Buku Teks