Davis, William G.
University of California Press, 1973
Buku Teks
Black, Christopher F., author
Routledge, 2001
Buku Teks
Gregg, Pauline, author
George G. Harrap, 1952
Buku Teks
Epstein, T. Scarlett, author
Manchester University Press , 1962
Buku Teks
ESCAP , 1975
Buku Teks