Schuman, David
Macmillan, 1976
Buku Teks
Vanessa Bainbridge ... [et al.]
International Institute for Environment and Development, 2000
Buku Teks
Schuman, David
Macmillan Publishing Company, 1976
Buku Teks
Page, Edward, 1953-, author
Harvester Wheatsheaf, 1992
Buku Teks
Dunleavy, Patrick
N.Y. Harvester , 1991
Buku Teks