Organization for Economic Co-operation and Development, 1972
Buku Teks
Hammersley, Martyn, author
Paul Chapman Publishing, 2002
Buku Teks
Blackwell Publishing, 2007
Buku Teks
pluto Press, 1990
Buku Teks
by Edwin Mansfield [and others]
Macmillan, 1971
Buku Teks