United Nations Environment Programme
Nettlap, 1993
Buku Referensi
Grant, W.D., author
Blackie, 1981
Buku Teks
Madjelis Ilmu Pengetahuan Indonesia
Madjelis Ilmu Pengetahuan Indonesia, 1959
Buku Referensi
edited by John E. Hay
United Nations Environment Programme, 1995
Buku Teks
edited by John E. Hay, Wimala Ponniah and Mahesh Pradhan
United Nations Environment Programme , 1995
Buku Teks