Ballard, Robert D.
Exploring our living planet
National Geographic Society, 1983
 Buku Referensi
Ahrens, L.H.
Distribution of the element in our planet
McGraw-Hill, 1965
 Buku Teks SO
Our planet, our health : report of the WHO Commission on Health and Environment. / WHO Commission on Health and Environment.
World Health Organization, 1992
 Buku Teks
Edel, May
The story of our ancestors
Little, Brown, 1955
 Buku Teks
Moon, Glenn W.
Story of our land and people
Holt, Rinehart and Winston, 1964
 Buku Teks SO